Gonzalez et al.

Journal of Cloud Computing: Advances, Systems and Applications 2012, 1:11

http://www.journalofcloudcomputing.com/content/1/1/11

R ESEA R CH Open Access

A quantitative analysis of current security

concerns and solutions for cloud computing
Nelson Gonzalez1* , Charles Miers1,4 , Fernando Redı́golo1 , Marcos Simplı́cio1 , Tereza Carvalho1 ,
Mats Näslund2 and Makan Pourzandi3

Abstract
The development of cloud computing services is speeding up the rate in which the organizations outsource their
computational services or sell their idle computational resources. Even though migrating to the cloud remains a
tempting trend from a financial perspective, there are several other aspects that must be taken into account by
companies before they decide to do so. One of the most important aspect refers to security: while some cloud
computing security issues are inherited from the solutions adopted to create such services, many new security
questions that are particular to these solutions also arise, including those related to how the services are organized
and which kind of service/data can be placed in the cloud. Aiming to give a better understanding of this complex
scenario, in this article we identify and classify the main security concerns and solutions in cloud computing, and
propose a taxonomy of security in cloud computing, giving an overview of the current status of security in this
emerging technology.

Introduction (SaaS, PaaS, and IaaS) and deployment (private, public,

Security is considered a key requirement for cloud com- community, and hybrid).
puting consolidation as a robust and feasible multi- Due to the ever growing interest in cloud computing,
purpose solution [1]. This viewpoint is shared by many there is an explicit and constant effort to evaluate the
distinct groups, including academia researchers [2,3], current trends in security for such technology, consider-
business decision makers [4] and government organi- ing both problems already identified and possible solu-
zations [5,6]. The many similarities in these perspec- tions [10]. An authoritative reference in the area is the
tives indicate a grave concern on crucial security and risk assessment developed by ENISA (European Network
legal obstacles for cloud computing, including service and Information Security Agency) [5]. Not only does
availability, data confidentiality, provider lock-in and it list risks and vulnerabilities, but it also offers a sur-
reputation fate sharing [7]. These concerns have their vey of related works and research recommendations. A
origin not only on existing problems, directly inherited similarly work is the security guidance provided by the
from the adopted technologies, but are also related to Cloud Security Alliance (CSA) [6], which defines security
new issues derived from the composition of essential domains congregating specific functional aspects, from
cloud computing features like scalability, resource shar- governance and compliance to virtualization and iden-
ing and virtualization (e.g., data leakage and hypervisor tity management. Both documents present a plethora of
vulnerabilities) [8]. The distinction between these classes security concerns, best practices and recommendations
is more easily identifiable by analyzing the definition of the regarding all types of services in NIST’s SPI model, as well
essential cloud computing characteristics proposed by the as possible problems related to cloud computing, encom-
NIST (National Institute of Standards and Technology) passing from data privacy to infrastructural configuration.
in [9], which also introduces the SPI model for services Albeit valuable, these studies do not focus on quantifying
their observations, something important for developing
a comprehensive understanding of the challenges still
*Correspondence: nmimura@larc.usp.br
1 Escola Politécnica at the University of São Paulo (EPUSP), São Paulo, Brazil undermining the potential of cloud computing.
Full list of author information is available at the end of the article

© 2012 Gonzalez et al.; licensee Springer. This is an Open Access article distributed under the terms of the Creative Commons
Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction
in any medium, provided the original work is properly cited.
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The main goal of this article is to identify, classify, and allowing them to extend local strategies to any
organize and quantify the main security concerns and remote resource or process [14].
solutions associated to cloud computing, helping in the
task of pinpointing the concerns that remain unanswered. (a) Transfer security: Distributed architectures,
Aiming to organize this information into a useful tool massive resource sharing and virtual machine
for comparing, relating and classifying already identi- (VM) instances synchronization imply more
fied concerns and solutions as well as future ones, we data in transit in the cloud, thus requiring
also present a taxonomy proposal for cloud comput- VPN mechanisms for protecting the system
ing security. We focus on issues that are specific to against sniffing, spoofing, man-in-the-middle
cloud computing, without losing sight of important issues and side-channel attacks.
that also exist in other distributed systems. This article (b) Firewalling: Firewalls protect the provider’s
extends our previous work presented in [11], providing an internal cloud infrastructure against insiders
enhanced review of the cloud computing security taxon- and outsiders [15]. They also enable VM
omy previously presented, as well as a deeper analysis of isolation, fine-grained filtering for addresses
the related work by discussing the main security frame- and ports, prevention of Denial-of-Service
works currently available; in addition, we discuss further (DoS) and detection of external security
the security aspects related to virtualization in cloud assessment procedures. Efforts for developing
computing, a fundamental yet still underserved field of consistent firewall and similar security
research. measures specific for cloud environments
[16,17] reveal the urge for adapting existing
Cloud computing security solutions for this new computing paradigm.
Key references such as CSA’s security guidance [6] and (c) Security configuration: Configuration of
top threats analysis [12], ENISA’s security assessment [5] protocols, systems and technologies to
and the cloud computing definitions from NIST [9] high- provide the required levels of security and
light different security issues related to cloud computing privacy without compromising performance
that require further studies for being appropriately han- or efficiency [18].
dled and, consequently, for enhancing technology accep-
2. Interfaces: Concentrates all issues related to user,
tance and adoption. Emphasis is given to the distinction
administrative and programming interfaces for using
between services in the form of software (SaaS), platform
and controlling clouds.
(PaaS) and infrastructure (IaaS), which are commonly
used as the fundamental basis for cloud service classifica- (a) API: Programming interfaces (essential to
tion. However, no other methods are standardized or even IaaS and PaaS) for accessing virtualized
employed to organize cloud computing security aspects resources and systems must be protected in
apart from cloud deployment models, service types or order to prevent malicious use [19-23].
traditional security models. (b) Administrative interface: Enables remote
Aiming to concentrate and organize information related control of resources in an IaaS (VM
to cloud security and to facilitate future studies, in this management), development for PaaS (coding,
section we identify the main problems in the area and deploying, testing) and application tools for
group them into a model composed of seven categories, SaaS (user access control, configurations).
based on the aforementioned references . Namely, the (c) User interface: End-user interface for
categories are: network security, interfaces, data secu- exploring provided resources and tools (the
rity, virtualization, governance, compliance and legal service itself), implying the need of adopting
issues. Each category includes several potential security measures for securing the environment
problems, resulting in a classification with subdivisions [24-27].
that highlights the main issues identified in the base (d) Authentication: Mechanisms required to
references: enable access to the cloud [28]. Most services
rely on regular accounts [20,29,30]
1. Network security: Problems associated with network consequently being susceptible to a plethora
communications and configurations regarding cloud of attacks [31-35] whose consequences are
computing infrastructures. The ideal network boosted by multi-tenancy and resource
security solution is to have cloud services as an sharing.
extension of customers’ existing internal networks
[13], adopting the same protection measures and 3. Data security: Protection of data in terms of
security precautions that are locally implemented confidentiality, availability and integrity (which can
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be applied not only to cloud environments, but any machine, which also enables other
solution requiring basic security levels) [36]. isolation-related attacks.

(a) Cryptography: Most employed practice to 5. Governance: Issues related to (losing) administrative
secure sensitive data [37], thoroughly and security controls in cloud computing solutions
required by industry, state and federal [45,46].
regulations [38].
(b) Redundancy: Essential to avoid data loss. (a) Data control: Moving data to the cloud means
Most business models rely on information losing control over redundancy, location, file
technology for its core functionalities and systems and other relevant configurations.
processes [39,40] and, thus, mission-critical (b) Security control: Loss of governance over
data integrity and availability must be security mechanisms and policies, as terms of
ensured. use prohibit customer-side vulnerability
(c) Disposal: Elementary data disposal assessment and penetration tests while
techniques are insufficient and commonly insufficient Service Level Agreements (SLA)
referred as deletion [41].In the cloud, the lead to security gaps.
complete destruction of data, including log (c) Lock-in: User potential dependency on a
references and hidden backup registries, is an particular service provider due to lack of
important requirement [42]. well-established standards (protocols and
4. Virtualization: Isolation between VMs, hypervisor data formats), consequently becoming
vulnerabilities and other problems associated to the particularly vulnerable to migrations and
use of virtualization technologies [43]. service termination.

(a) Isolation: Although logically isolated, all VMs 6. Compliance: Includes requirements related to service
share the same hardware and consequently availability and audit capabilities [47,48].
the same resources, allowing malicious
entities to exploit data leaks and cross-VM (a) Service Level Agreements (SLA):
attacks [44]. The concept of isolation can also Mechanisms to ensure the required service
be applied to more fine-grained assets, such availability and the basic security procedures
as computational resources, storage and to be adopted [49].
memory. (b) Loss of service: Service outages are not
(b) Hypervisor vulnerabilities: The hypervisor is exclusive to cloud environments but are
the main software component of more serious in this context due to the
virtualization. Even though there are known interconnections between services (e.g., a
security vulnerabilities for hypervisors, SaaS using virtualized infrastructures
solutions are still scarce and often provided by an IaaS), as shown in many
proprietary, demanding further studies to examples [50-52]. This leads to the need of
harden these security aspects. strong disaster recovery policies and provider
(c) Data leakage: Exploit hypervisor recommendations to implement
vulnerabilities and lack of isolation controls customer-side redundancy if applicable.
in order to leak data from virtualized (c) Audit: Allows security and availability
infrastructures, obtaining sensitive customer assessments to be performed by customers,
data and affecting confidentiality and providers and third-party participants.
integrity. Transparent and efficient methodologies are
(d) VM identification: Lack of controls for necessary for continuously analyzing service
identifying virtual machines that are being conditions [53] and are usually required by
used for executing a specific process or for contracts or legal regulations. There are
storing files. solutions being developed to address this
(e) Cross-VM attacks: Includes attempts to problem by offering a transparent API for
estimate provider traffic rates in order to automated auditing and other useful
steal cryptographic keys and increase chances functionalities [54].
of VM placement attacks. One example (d) Service conformity: Related to how
consists in overlapping memory and storage contractual obligations and overall service
regions initially dedicated to a single virtual requirements are respected and offered based
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on the SLAs predefined and basic service and cloud. It also comprises security during transferences of
customer needs. data and virtual machines, as well as other virtualization
related issues, such as isolation and cross-VM attacks.
7. Legal issues: Aspects related to judicial requirements This organization is depicted in Figure 2. The architec-
and law, such as multiple data locations and privilege ture group allows a clearer division of responsibilities
management. between providers and customers, and also an analysis
of their security roles depending on the type of service
(a) Data location: Customer data held in offered (Software, Platform or Infrastructure). This sug-
multiple jurisdictions depending on gests that the security mechanisms used must be clearly
geographic location [55] are affected, directly stated before the service is contracted, defining which
or indirectly, by subpoena law-enforcement role is responsible for providing firewalling capabilities,
measures. access control features and technology-specific require-
(b) E-discovery: As a result of a law-enforcement ments (such as those related to virtualization).
measures, hardware might be confiscated for The compliance dimension introduces responsibilities
investigations related to a particular toward services and providers. The former includes SLA
customer, affecting all customers whose data concerns, loss of service based on outages and chain fail-
were stored in the same hardware [56-58]. ures, and auditing capabilities as well as transparency and
Data disclosure is critical in this case. security assessments. The latter refers to loss of control
(c) Provider privilege: Malicious activities of over data and security policies and configurations, and
provider insiders are potential threats to also lock-in issues resulting from lack of standards, migra-
confidentiality, availability and integrity of tions and service terminations. The complete scenario is
customers’ data and processes’ information presented in Figure 3.
[59,60]. The privacy dimension includes data security itself
(d) legislation: Juridical concerns related to new (from sensitive data, regulations and data loss to dis-
concepts introduced by cloud computing posal and redundancy) and legal issues (related to multiple
[61]. jurisdictions derived from different locations where data
and services are hosted). The expansion of this group is
Cloud computing security taxonomy represented in Figure 4. We note that the concerns in this
The analysis of security concerns in the context of cloud dimension cover the complete information lifecycle (i.e.,
computing solutions shows that each issue brings differ- generation, use, transfer, transformation, storage, archiv-
ent impacts on distinct assets. Aiming to create a security ing, and destruction) inside the provider perimeter and in
model both for studying security aspects in this context its immediate boundaries (or interfaces) to the users.
and for supporting decision making, in this section we A common point between all groups is the intrinsic con-
consider the risks and vulnerabilities previously presented nection to data and service lifecycles. Both privacy and
and arrange them in hierarchical categories, thus creating compliance must be ensured through all states of data,
a cloud security taxonomy. The main structure of the pro- including application information or customer assets,
posed taxonomy, along with its first classification levels, while security in this case is more oriented towards how
are depicted in Figure 1. the underlying elements (e.g., infrastructural hardware
The three first groups correspond to fundamental (and and software) are protected.
often related) security principles [7] (Chapters 3-8).
The architecture dimension is subdivided into network Current status of cloud security
security, interfaces and virtualization issues, comprising A clear perspective of the main security problems regard-
both user and administrative interfaces to access the ing cloud computing and on how they can be organized

Figure 1 Cloud computing security taxonomy. Top level overview of the security taxonomy proposed, highlighting the three main categories:
security related to privacy, architecture and compliance.
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Figure 2 Security taxonomy - architecture. Details from architecture category, which is divided in network, host, application, data (security and
storage), security management, and identity and access controls – all these elements are directly connected to the infrastructure and architecture
adopted to implement or use a cloud solution.

to ease decision making is the primary step for having problems and solutions by evaluating the number of cita-
a comprehensive overview of the current status of cloud tions for each case. We used a quantitative approach to
security. In this section, we analyze industry and academia identify the amount of references related to each category
viewpoints focusing on strategic study areas that need of concerns or solutions. Our goal is not to determine
to be further developed. This study is based on more if the presented solutions completely solve an identified
than two hundred different references including white concern, since most of the referenced authors agree that
papers, technical reports, scientific papers and other rele- this is an involved task. Nonetheless, we identify the num-
vant publications. They were analyzed in terms of security ber of references dealing with each concern, providing
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Figure 3 Security taxonomy - compliance. Details from compliance category, divided in lifecycle controls and governance, risk and other
compliance related issues (such as continuous improvement policies).

Figure 4 Security taxonomy - privacy. Details from privacy category, initially divided in concerns and principles. Concerns are related to the
complete data lifecycle, from generation, use and transfer to transformation, storage, archival and destruction. Principles are guidelines related to
privacy in the cloud.
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some useful insight on which are the concerns that have Therefore, one reference can produce more than one
received more attention from the research community entry on each specified category.
and which have not been so extensively analyzed. Some 3. Some security perspectives were not covered in this
observations about the analysis method: paper, as each security/concern category can be
sub-divided in finer-grained aspects such as:
1. The references consulted came from different authentication, integrity, network communications,
research segments, including academia, etc.
organizations, and companies. Due to the article’s
length limitations, we did not include all the We present the security concerns and solutions using
consulted references in the References section. In the pie charts in order to show the representativeness of each
following we present some of the main sources of category/group in the total amount of references identi-
consultation: fied. The comparison between areas is presented using
radar graphs to identify how many solutions address each
(a) Academia: conference papers and journals
concern category/group.
published by IEEE, ACM, Springer,
Webscience, and Scipress.
Security concerns
(b) Organizations: reports, white papers, and
interviews from SANS Institute, CSA, NIST, The results obtained for the number of citations on secu-
ENISA, Gartner Group, KVM.org, rity issues is shown in Figure 5. The three major problems
OpenGrid, OpenStack, and OpenNebula. identified in these references are legal issues, compliance
(c) Companies: white papers, manuals, and loss of control over data. These legal- and governance-
interviews, and web content from related concerns are followed by the first technical issue,
ERICSSON, IBM, XEROX, Cisco, VMWare, isolation, with 7% of citations. The least cited problems
XEN, CITRIX, EMC, Microsoft, and are related to security configuration concerns, loss of ser-
Salesforce. vice (albeit this is also related to compliance, which is a
major problem), firewalling and interfaces.
2. Each reference was analyzed aiming to identify all the Grouping the concerns using the categories presented
mentioned concerns covered and solutions provided. in section “Cloud computing security” leads to the

Figure 5 Security problems. Pie chart for security concerns.

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Figure 6 Security problems with grouped categories. Pie chart for security concerns with grouped categories (seven altogether: legal issues,
compliance, governance, virtualization, data security, interfaces and network security).

Figure 7 Security solutions with grouped categories. Pie chart for solutions with grouped categories, showing a clear lack for virtualization
security mechanisms in comparison to its importance in terms of concerns citations.
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construction of Figure 6. This figure shows that legal and (respectively 24%, 22%, and 17%); however, the same also
governance issues represent a clear majority with 73% of happens when we consider the number of references
concern citations, showing a deep consideration of legal proposing solutions for those issues (which represent
issues such as data location and e-discovery, or gover- respectively 29%, 27%, and 14% of the total number of
nance ones like loss of control over security and data. The citations). In other words, these concerns are higly rele-
technical issue more intensively evaluated (12%) is virtual- vant but a large number solutions are already available for
ization, followed by data security, interfaces and network tackling them.
security. The situation is completely different when we analyze
Virtualization is one of the main novelties employed by technical aspects such as virtualization, isolation and data
cloud computing in terms of technologies employed, con- leakage. Indeed, virtualization amounts for 12% of prob-
sidering virtual infrastructures, scalability and resource lem references and only 3% for solutions. Isolation is a
sharing, and its related problems represent the first major perfect example of such discrepancy as the number of
technical concern. citations for such problems represents 7% in Figure 5,
while solutions correspond to only 1% of the graph from
Security solutions Figure 8. We note that, for this specific issue, special care
When analyzing citations for solutions, we used the same has been taken when assessing the most popular virtual
approach described in the beginning of this section. The machine solution providers (e.g., XEN, VMWARE, and
results are presented in Figure 7, which shows the percent- KVM) aiming to verify their concerns and available solu-
age of solutions in each category defined in section “Cloud tions. A conclusion that can be drawn from this situation
computing security”, and also in Figure 8, which highlights is that such concerns are also significant but yet little is
the contribution of each individual sub-category. available in terms of solutions. This indicates the need of
When we compare Figures 6 and 7, it is easy to observe evaluating potential areas still to be developed in order
that the number of citations covering security problems to provide better security conditions when migrating data
related to legal issues, compliance and governance is high and processes in the cloud.

Figure 8 Security solutions. Pie chart for solutions citations.

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Comparison capabilities), hypervisor vulnerabilities, data leakage,

The differences between problem and solution citations cross-VM attacks and VM identification. The contrast
presented in the previous sections can be observed in related to isolation and cross-VM attacks is more evident
Figure 9. than for the other issues. However, the number of solution
Axis values correspond to the number of citations found citations for all issues is notably low if compared to any
among the references studied. Blue areas represent con- other security concern, reaffirming the need for further
cern citations and lighter red indicates solutions, while researches in those areas.
darker red shows where those areas overlap. In other
words, light red areas are problems with more citations Related work
for solutions than problems – they might be meaningful An abundant number of related works and publications
problems, but there are many solutions already addressing exist in the literature, emphasizing the importance and
them – while blue areas represent potential subjects that demand of security solutions for cloud computing. How-
have received little attention so far, indicating the need for ever, we did not identify any full taxonomy that addresses
further studies. directly the security aspects related to cloud comput-
Figure 9 clearly shows the lack of development regard- ing. We only identified some simplified models that
ing data control mechanisms, hypervisor vulnerabilities were developed to cover specific security aspects such as
assessment and isolation solutions for virtualized envi- authentication. We were able to recognize two main types
ronments. On the other hand, areas such as legal con- of works: (1) security frameworks, which aim to aggregate
cerns, SLAs, compliance and audit policies have a quite information about security and also to offer sets of best
satisfactory coverage. The results for grouped categories practices and guidelines when using cloud solutions, and
(presented in section 4) are depicted in Figure 10. (2) publications that identify future trends and propose
Figure 10 shows that virtualization problems represent solutions or areas of interest for research. Each category
an area that requires studies for addressing issues such as and corresponding references are further analyzed in the
isolation, data leakage and cross-VM attacks; on the other following subsections.
hand, areas such as compliance and network security
encompass concerns for which there are already a con- Security frameworks
siderable number of solutions or that are not considered Security frameworks concentrate information on security
highly relevant. and privacy aiming to provide a compilation of risks, vul-
Finally, Considering virtualization as key element for nerabilities and best practices to avoid or mitigate them.
future studies, Figure 11 presents a comparison focus- There are several entities that are constantly publishing
ing on five virtualization-related problems: isolation (of material related to cloud computing security, including
computational resources, such as memory and storage ENISA, CSA, NIST, CPNI (Centre for the Protection of

Figure 9 Comparison between citations. Radar chart comparing citations related to concerns and solutions, showing the disparities for each
security category adopted.
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Figure 10 Comparison between citations with grouped categories. Radar chart grouping the categories, showing the difference between
citations about concerns and solutions regarding each category.

National Infrastructure from UK government) and ISACA and risks related to its use [5]. In this study, the security
(the Information Systems Audit and Control Association). risks are divided in four categories:
In this paper we focus on the first three entities, which
by themselves provide a quite comprehensive overview of
issues and solutions and, thus, allowing a broad under- • Policy and organizational: issues related to
standing of the current status of cloud security. governance, compliance and reputation;
• Technical: issues derived from technologies used to
ENISA implement cloud services and infrastructures, such as
ENISA is an agency responsible for achieving high and isolation, data leakage and interception, denial of
effective level of network and information security within service attacks, encryption and disposal;
the European Union [62]. In the context of cloud comput- • Legal: risks regarding jurisdictions, subpoena and
ing, they published an extensive study covering benefits e-discovery;

Figure 11 Comparison for virtualization. Radar chart only for virtualization issues.
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• Not cloud specific: other risks that are not unique to 5. Portability and interoperability: ability to change
cloud environments, such as network management, providers, services or bringing back data to local
privilege escalation and logging; premises without major impacts;
6. Traditional security, business continuity and disaster
As a top recommendation for security in cloud com- recovery: the influence of cloud solutions on
puting, ENISA suggests that providers must ensure some traditional processes applied for addressing security
security practices to customers and also a clear contract to needs;
avoid legal problems. Key points to be developed include 7. Data center operations: analyzing architecture and
breach reporting, better logging mechanisms and engi- operations from data centers and identifying
neering of large scale computer systems, which encom- essential characteristics for ensuring stability;
pass the isolation of virtual machines, resources and 8. Incident response, notification and remediation:
information. Their analysis is based not only on what is policies for handling incidents;
currently observed, but also on what can be improved 9. Application security: aims to identify the possible
through the adoption of existing best practices or by security issues raised from migrating a specific
means of solutions that are already used in non-cloud solution to the cloud and which platform (among SPI
environments. This article aims at taking one step fur- model) is more adequate;
ther by transforming these observations into numbers – a 10. Encryption and key management: how higher
quantitative approach. scalability via infrastructure sharing affects
encryption and other mechanisms used for
CSA protecting resources and data;
CSA is an organization led by a coalition of industry 11. Identity and access management: enabling
practitioners, corporations, associations and other stake- authentication for cloud solutions while maintaining
holders [63], such as Dell, HP and eBay. One of its main security levels and availability for customers and
goals is to promote the adoption of best practices for organizations;
providing security within cloud computing environments. 12. Virtualization: risks related to multi-tenancy,
Three CSA documents are analyzed in this paper – the isolation, virtual machine co-residence and
security guidance [6], the top threats in cloud computing hypervisor vulnerabilities, all introduced by
[12] and the Trusted Cloud Initiative (TCI) architecture virtualization technologies;
[64] – as they comprise most of the concepts and guide- 13. Security as a service: third party security
lines researched and published by CSA. mechanisms, delegating security responsibilities to a
The latest CSA security guidance (version 3.0 [65]) trusted third party provider;
denotes multi-tenancy as the essential cloud characteristic
while virtualization can be avoided when implementing CSA also published a document focusing on identify-
cloud infrastructures – multi-tenancy only implies the ing top threats, aiming to aid risk management strategies
use of shared resources by multiple consumers, possibly when cloud solutions are adopted [12]. As a complete
from different organizations or with different objectives. list of threats and pertinent issues is countless, the doc-
They discuss that, even if virtualization-related issues ument targets those that are specific or intensified by
can be circumvented, segmentation and isolated policies fundamental characteristics of the cloud, such as shared
for addressing proper management and privacy are still infrastructures and greater flexibility. As a result, seven
required. The document also establishes thirteen security threats were selected:
domains:
1. Abuse and nefarious used of cloud computing: while
1. Governance and risk management: ability to measure providing flexible and powerful resources and tools,
the risk introduced by adopting cloud computing IaaS and PaaS solutions also unveil critical
solutions, such as legal issues, protection of sensitive exploitation possibilities built on anonymity. This
data and their relation to international boundaries; leads to abuse and misuse of the provided
2. Legal issues: disclosure laws, shared infrastructures infrastructure for conducting distributed denial of
and interference between different users; service attacks, hosting malicious data, controlling
3. Compliance and audit: the relationship between botnets or sending spam;
cloud computing and internal security policies; 2. Insecure application programming interfaces: cloud
4. Information management and data security: services provide APIs for management, storage,
identification and control of stored data, loss of virtual machine allocation and other service-specific
physical control of data and related policies to operations. The interfaces provided must implement
minimize risks and possible damages; security methods to identify, authenticate and protect
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against accidental or malicious use, which can human resources security, security monitoring services,
introduce additional complexities to the system such legal services and internal investigations; TOGAF defines
as the need for third-party authorities and services; the types of services covered (presentation, application,
3. Malicious insiders: although not specific to cloud information and infrastructure; ITIL is used for informa-
computing, its effects are amplified by the tion technology operation and support, from IT oper-
concentration and interaction of services and ation to service delivery, support and management of
management domains; incidents, changes and resources; finally, Jericho cov-
4. Shared technology vulnerabilities: scalability ers security and risk management, including information
provided by cloud solutions are based on hardware security management, authorization, threat and vulnera-
and software components which are not originally bility management, policies and standards. The result is a
designed to provide isolation. Even though tri-dimensional relationship between cloud delivery, trust
hypervisors offer an extra granularity layer, they still and operation that aims to be easily consumed and applied
exhibit flaws which are exploited for privilege in a security-oriented design.
escalation;
5. Data loss and leakage: insufficient controls NIST
concerning user access and data security (including NIST has recently published a taxonomy for security in
privacy and integrity), as well as disposal and even cloud computing [67] that is comparable to the taxonomy
legal issues; introduced in section “Cloud computing security taxon-
6. Account, service and traffic hijacking: phishing and omy”. This taxonomy’s first level encompass typical roles
related frauds are not a novelty to computing in the cloud environment: cloud service provider, respon-
security. However, not only an attacker is able to sible for making the service itself available; cloud service
manipulate data and transactions, but also to use consumer, who uses the service and maintains a business
stolen credentials to perform other attacks that relationship with the provider; cloud carrier, which pro-
compromise customer and provider reputation. vides communication interfaces between providers and
7. Unknown risk profile: delegation of control over data consumers; cloud broker, that manages use, performance
and infrastructure allows companies to better and delivery of services and intermediates negotiations
concentrate on their core business, possibly between providers and consumers; and cloud auditor,
maximizing profit and efficiency. On the other hand, which performs assessment of services, operations and
the consequent loss of governance leads to obscurity security. Each role is associated to their respective activ-
[66]: information about other customers sharing the ities and decomposed on their components and subcom-
same infrastructure or regarding patching and ponents. The clearest difference from our taxonomy is the
updating policies is limited. This situation creates hierarchy adopted, as our proposal primarily focuses on
uncertainty concerning the exact risk levels that are security principles in its higher level perspective, while
inherent to the cloud solution; the cloud roles are explored in deeper levels. The con-
cepts presented here extend NIST’s initial definition for
It is interesting to notice the choice for cloud-specific cloud computing [9], incorporating a division of roles and
issues as it allows the identification of central points responsibilities that can be directly applied to security
for further development. Moreover, this compilation of assessments. On the other hand, NIST’s taxonomy incor-
threats is closely related to CSA security guidance, com- porates concepts such as deployment models, service
posing a solid framework for security and risk analysis types and activities related to cloud management (porta-
assessments while providing recommendations and best bility, interoperability, provisioning), most of them largely
practices to achieve acceptable security levels. employed in publications related to cloud computing –
Another approach adopted by CSA for organizing infor- including this one.
mation related to cloud security and governance is the
TCI Reference Architecture Model [64]. This document Frameworks summary
focuses on defining guidelines for enabling trust in the Tables 1 and 2 summarize the information about each
cloud while establishing open standards and capabilities framework.
for all cloud-based operations. The architecture defines
different organization levels by combining frameworks Books, papers and other publications
like the SPI model, ISO 27002, COBIT, PCI, SOX and Rimal, Choi and Lumb [3] present a cloud taxonomy
architectures such as SABSA, TOGAF, ITIL and Jeri- created from the perspective of the academia, developers
cho. A wide range of aspects are then covered: SABSA and researchers, instead of the usual point of view related
defines business operation support services, such as com- to vendors. Whilst they do provide definitions and con-
pliance, data governance, operational risk management, cepts such as cloud architecture (based on SPI model),
Gonzalez et al. Journal of Cloud Computing: Advances, Systems and Applications 2012, 1:11 Page 14 of 18
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Table 1 Summary of CSA security frameworks

Framework Objectives Structure and comments
CSA Guidance
• Recommendations for reducing risks • One architectural domain
• No restrictions regarding specific • Governance domains: risk management, legal concerns, compliance,
solutions or service types auditing, information management, interoperability and portability
• Guidelines not necessarily applicable • Operational domains: traditional and business security, disaster recovery,
for all deployment models data center operations, encryption, application security, identification,
• Provide initial structure to divide efforts authorization, virtualization, security outsourcing
for researches • Emphasis on the fact that cloud is not bound to virtualization technologies,
though cloud services heavily depend on virtualized infrastructures to
provide flexibility and scalability

CSA Top Threats

• Provide context for risk management • Seven main threats:
decisions and strategies
• Focus on issues which are unique or – Abuse and malicious use of cloud resources
highly influenced by cloud computing – Insecure APIs
characteristics – Malicious insiders
– Shared technology vulnerabilities
– Data loss and leakage
– Hijacking of accounts, services and traffic
– Unknown risk profile (security obscurity)
• Summarizes information on top threats and provide examples, remediation
guidelines, impact caused and which service types (based on SPI model)
are affected

CSA Architecture
• Enable trust in the cloud based on • Four sets of frameworks (security, NIST SPI, IT audit and legislative) and four
well-known standards and certifications architectural domains (SABSA business architecture, ITIL for services
allied to security frameworks and other management, Jericho for security and TOGAF for IT reference)
open references • Tridimensional structure based on premises of cloud delivery, trust and
• Use widely adopted frameworks in operations
order to achieve standardization of • Concentrates a plethora of concepts and information related to services
policies and best practices based on operation and security
already accepted security principles

Table summarizing information related to CSA security frameworks (guidance, top threats and TCI architecture).

virtualization management, service types, fault tolerance discussed are the inadequate encryption and key manage-
policies and security, no further studies are developed ment capabilities currently offered, as well as the need for
focusing on cloud specific security aspects. This charac- multi-entity key management.
teristic is also observed in other cloud taxonomies [68-70] Many publications also state the need for better security
whose efforts converge to the definition of service models mechanisms for cloud environments. Doelitzscher et al.
and types rather than to more technical aspects such as [71] emphasize security as a major research area in cloud
security, privacy or compliance concerns – which are the computing. They also highlight the lack of flexibility of
focus of this paper. classic intrusion detection mechanisms to handle virtual-
In [7], Mather, Kumaraswamy and Latif discuss the ized environments, suggesting the use of special security
current status of cloud security and what is predicted audit tools associated to business flow modeling through
for the future. The result is a compilation of security- security SLAs. In addition, they identify abuse of cloud
related subjects to be developed in topics like infras- resources, lack of security monitoring in cloud infrastruc-
tructure, data security and storage, identity and access ture and defective isolation of shared resources as focal
management, security management, privacy, audit and points to be managed. Their analysis of top security con-
compliance. They also explore the unquestionable urge for cerns is also based on publications from CSA, ENISA and
more transparency regarding which party (customer or others, but after a quick evaluation of issues their focus
cloud provider) provides each security capability, as well switch to their security auditing solution, without offer-
as the need for standardization and for the creation of ing a deeper quantitative compilation of security risks and
legal agreements reflecting operational SLAs. Other issues areas of concern.
Gonzalez et al. Journal of Cloud Computing: Advances, Systems and Applications 2012, 1:11 Page 15 of 18
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Table 2 Summary of ENISA and NIST security frameworks

Framework Objectives Structure and comments
ENISA Report
• Study on benefits and risks when • Three main categories of cloud specific risks (policy and organizational,
adopting cloud solutions for business technical, legal) plus one extra category for not specific ones
operations • Offers basic guidelines and best practices for avoiding or mitigating their
• Provide information for security effects
assessments and decision making • Presents recommendations for further studies related to trust building
(certifications, metrics and transparency), large scale data protection
(privacy, integrity, incident handling and regulations) and technical
aspects (isolation, portability and resilience)
• Highlights the duality of scalability (fast, flexible and accessible resources
versus concentrations of data attracting attackers and also providing
infrastructure for aiding their operations)
• Extensive study on risks considering their impact and probability

NIST Taxonomy
• Define what cloud services should • Taxonomy levels:
provide rather than how to design and
implement solutions – First level: cloud roles (service provider, consumer, cloud broker,
• Ease the understanding of cloud cloud carrier and cloud auditor)
internal operations and mechanisms – Second level: activities performed by each role (cloud
management, service deployment, cloud access and service
consumption)
– Third and following levels: elements which compose each activity
(deployment models, service types and auditing elements)
• Based on publication SP 500-292, highlighting the importance of security,
privacy and levels of confidence and trust to increase technology
acceptance
• Concentrates many useful concepts, such as models for deploying or
classifying services

Table summarizing information on ENISA and NIST security frameworks.

Associations such as the Enterprise Strategy Group Finally, Chadwick and Casenove [75] describe a security
[72] emphasize the need for hypervisor security, shrink- API for federated access to cloud resources and authority
ing hypervisor footprints, defining the security perimeter delegation while setting fine-grained controls and guar-
virtualization, and linking security and VM provision- anteeing the required levels of assurance inside cloud
ing for better resource management. Aiming to address environments. These publications highlight the need of
these requirements, they suggest the use of increased security improvements related to virtual machines and
automation for security controls, VM identity manage- virtualization techniques, concern that this paper demon-
ment (built on top of Public Key Infrastructure and Open strates to be valid and urgent.
Virtualization Format) and data encryption (tightly con-
nected to state-of-art key management practices). Wallom Discussion
et al. [73] emphasize the need of guaranteeing virtual Considering the points raised in the previous section, a
machines’ trustworthiness (regarding origin and identity) straightforward conclusion is that cloud security includes
to perform security-critical computations and to han- old and well-known issues – such as network and other
dle sensitive data, therefore presenting a solution which infrastructural vulnerabilities, user access, authentication
integrates Trusted Computing technologies and avail- and privacy – and also novel concerns derived from
able cloud infrastructures. Dabrowski and Mills [74] used new technologies adopted to offer the adequate resources
simulation to demonstrate virtual machine leakage and (mainly virtualized ones), services and auxiliary tools.
resource exhaustion scenarios leading to degraded per- These problems are summarized by isolation and hypervi-
formance and crashes; they also propose the addition sor vulnerabilities (the main technical concerns according
of orphan controls to enable the virtualized cloud envi- to the studies and graphics presented), data location and
ronment to offer higher availability levels while keeping e-discovery (legal aspects), and loss of governance over
overhead costs under control. Ristenpart et al. [44] also data, security and even decision making (in which the
explore virtual machine exploitation focusing on informa- cloud must be strategically and financially considered as a
tion leakage, specially sensitive data at rest or in transit. decisive factor).
Gonzalez et al. Journal of Cloud Computing: Advances, Systems and Applications 2012, 1:11 Page 16 of 18
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Another point observed is that, even though adopt- A secure cloud computing environment depends on
ing a cloud service or provider may be easy, migrating several security solutions working harmoniously together.
to another is not [76]. After moving local data and pro- However, in our studies we did not identify any security
cesses to the cloud, the lack of standards for protocols solutions provider owning the facilities necessary to get
and formats directly affects attempts to migrate to a dif- high levels of security conformity for clouds. Thus, cloud
ferent provider even if this is motivated by legitimate rea- providers need to orchestrate / harmonize security solu-
sons such as non-fulfillment of SLAs, outages or provider tions from different places in order to achieve the desired
bankruptcy [77]. Consequently, the first choice must be security level.
carefully made, as SLAs are not perfect and services In order to verify these conclusions in practice, we
outages happen at the same pace that resource sharing, deployed testbeds using OpenNebula (based on KVM and
multi-tenancy and scalability are not fail proof. After a XEN) and analyzed its security aspects; we also analyzed
decision is made, future migrations between services can virtualized servers based on VMWARE using our testbed
be extremely onerous in terms of time and costs; most networks. This investigation lead to a wide research of
likely, this task will require an extensive work for bring- PaaS solutions, and allowed us to verify that most of them
ing all data and resources to a local infrastructure before use virtual machines based on virtualization technolo-
redeploying them into the cloud. gies such as VMWARE, XEN, and KVM, which often lack
Finally, the analysis of current trends for cloud comput- security aspects We also learned that Amazon changed
ing reveals that there is a considerable number of well- the XEN source code in order to include security fea-
studied security concerns, for which plenty solutions and tures, but unfortunately the modified code is not publicly
best practices have been developed, such as those related available and there appears to be no article detailing the
to legal and administrative concerns. On the other hand, changes introduced. Given these limitations, a deeper
many issues still require further research effort, especially study on current security solutions to manage cloud com-
those related to secure virtualization. puting virtual machines inside the cloud providers should
be a focus of future work in the area. We are also working
Considerations and future work on a testbed based on OpenStack for researches related
Security is a crucial aspect for providing a reliable envi- to identity and credentials management in the cloud envi-
ronment and then enable the use of applications in the ronment. This work should address basic needs for better
cloud and for moving data and business processes to security mechanisms in virtualized and distributed archi-
virtualized infrastructures. Many of the security issues tectures, guiding other future researches in the security
identified are observed in other computing environments: area.
authentication, network security and legal requirements,
Competing interests
for example, are not a novelty. However, the impact of The authors declare that they have no competing interests.
such issues is intensified in cloud computing due to
characteristics such as multi-tenancy and resource shar- Author’s contributions
NG carried out the security research, including the prospecting for information
ing, since actions from a single customer can affect all and references, categorization, results analysis, taxonomy creation and analysis
other users that inevitably share the same resources and of related work. CM participated in the drafting of the manuscript as well as in
interfaces. On the other hand, efficient and secure vir- the analysis of references, creation of the taxonomy and revisions of the text.
MS, FR, MN and MP participated in the critical and technical revisions of the
tualization represents a new challenge in such a context paper including the final one, also helping with the details for preparing the
with high distribution of complex services and web- paper to be published. TC coordinated the project related to the paper and
based applications, thus requiring more sophisticated also gave the final approval of the version to be published. All authors read
and approved the final manuscript.
approaches. At the same time, our quantitative analysis
indicates that virtualization remains an underserved area Acknowledgements
regarding the number of solutions provided to identified This work was supported by the Innovation Center, Ericsson
Telecomunicações S.A., Brazil.
concerns.
It is strategic to develop new mechanisms that pro- Author details
1 Escola Politécnica at the University of São Paulo (EPUSP), São Paulo, Brazil.
vide the required security level by isolating virtual 2 Ericsson Research, Stockholm, Sweden. 3 Ericsson Research, Ville Mont-Royal,
machines and the associated resources while following Canada. 4 State University of Santa Catarina, Joinville, Brazil.
best practices in terms of legal regulations and compli-
ance to SLAs. Among other requirements, such solutions Received: 30 January 2012 Accepted: 5 June 2012
Published: 12 July 2012
should employ virtual machine identification, provide
an adequate separation of dedicated resources com- References
bined with a constant observation of shared ones, and 1. IDC (2009) Cloud Computing 2010 – An IDC Update.
slideshare.net/JorFigOr/cloud-computing-2010-an-idc-update
examine any attempt of exploiting cross-VM and data 2. Armbrust M, Fox A, Griffith R, Joseph AD, Katz RH, Konwinski A, Lee G,
leakage. Patterson DA, Rabkin A, Stoica I, Zaharia M (2009) Above the Clouds:
Gonzalez et al. Journal of Cloud Computing: Advances, Systems and Applications 2012, 1:11 Page 17 of 18
http://www.journalofcloudcomputing.com/content/1/1/11

A Berkeley View of Cloud Computing. Technical Report 27. Salesforce (2011) Security Implementation Guide.
UCB/EECS-2009-28, University of California at Berkeley, login.salesforce.com/help/doc/en/salesforce security impl guide.pdf
eecs.berkeley.edu/Pubs/TechRpts/2009/EECS-2009-28.html 28. Li H, Dai Y, Tian L, Yang H (2009) Identity-Based Authentication for Cloud
3. Rimal BP, Choi E, Lumb I (2009) A Taxonomy and, Survey of Cloud Computing. In: Proceedings of the 1st International Conference on Cloud
Computing Systems. In: Fifth International Joint Conference on INC, IMS Computing, CloudCom ’09
and IDC, NCM ’09, CPS. pp 44–51 29. Amazon (2011) Elastic Compute Cloud (EC2). aws.amazon.com/ec2/
4. Shankland S (2009) HP’s Hurd dings cloud computing, IBM. 30. Kaufman C, Venkatapathy R (2010) Windows Azure Security Overview.
CNET News go.microsoft.com/?linkid=9740388, [August]
5. Catteddu D, Hogben G (2009) Benefits, risks and recommendations for 31. McMillan R (2010) Google Attack Part of Widespread Spying Effort.
information security. Tech. rep., European Network and Information PCWorld
Security Agency, enisa.europa.eu/act/rm/files/deliverables/cloud- 32. Mills E (2010) Behind the China attacks on Google. CNET News
computing-risk-assessment 33. Arrington M (2010) Google Defends Against Large Scale Chinese Cyber
6. CSA (2009) Security Guidance for Critical Areas of Focus in Cloud Attack: May Cease Chinese Operations. TechCrunch
Computing. Tech. rep., Cloud Security Alliance 34. Bosch J (2009) Google Accounts Attacked by Phishing Scam. BrickHouse
7. Mather T, Kumaraswamy S (2009) Cloud Security and privacy: An Security Blog
Enterprise Perspective on Risks and Compliance. 1st edition. O’Reilly 35. Telegraph T (2009) Facebook Users Targeted By Phishing Attack. The
Media Telegraph
8. Chen Y, Paxson V, Katz RH (2010) What’s New About Cloud Computing 36. Pearson S (2009) Taking account of privacy when designing cloud
Security? Technical Report UCB/EECS-2010-5, University of California at computing services. In: Proceedings of the 2009 ICSE Workshop on
Berkeley, eecs.berkeley.edu/Pubs/TechRpts/2010/EECS-2010-5.html Software Engineering Challenges of Cloud Computing, CLOUD ’09
9. Mell P, Grance T (2009) The NIST Definition of Cloud Computing. 37. Musthaler L (2009) Cost-effective data encryption in the cloud. Network
Technical Report 15, National Institute of Standards and Technology, World
www.nist.gov/itl/cloud/upload/cloud-def-v15.pdf 38. Yan L, Rong C, Zhao G (2009) Strengthen Cloud Computing Security with
10. Ibrahim AS, Hamlyn-Harris J, Grundy J (2010) Emerging Security Federal Identity Management Using Hierarchical Identity-Based
Challenges of Cloud Virtual Infrastructure. In: Proceedings of APSEC 2010 Cryptography. In: Proceedings of the 1st International Conference on
Cloud Workshop, APSEC ’10 Cloud Computing, CloudCom ’09
11. Gonzalez N, Miers C, Redı́golo F, Carvalho T, Simplı́cio M, Naslund M, 39. Tech C (2010) Examining Redundancy in the Data Center Powered by the
Pourzandi M (2011) A quantitative analysis of current security concerns Cloud and Disaster Recovery. Consonus Tech
and solutions for cloud computing. In: Proceedings of 3rd IEEE 40. Lyle M (2011) Redundancy in Data Storage. Define the Cloud
CloudCom. Athens/Greece: IEEE Computer Society 41. Dorion P (2010) Data destruction services: When data deletion is not
12. Hubbard D, Jr LJH, Sutton M (2010) Top Threats to Cloud Computing. enough. SearchDataBackup.com
Tech. rep., Cloud Security Alliance. cloudsecurityalliance.org/research/ 42. Mogull R (2009) Cloud Data Security: Archive and Delete (Rough Cut).
projects/top-threats-to-cloud-computing/ securosis.com/blog/cloud-data-security-archive-and-delete-rough-cut/
13. Tompkins D (2009) Security for Cloud-based Enterprise Applications. 43. Messmer E (2011) Gartner: New security demands arising for
http://blog.dt.org/index.php/2009/02/security-for-cloud-based- virtualization, cloud computing. http://www.networkworld.com/news/
enterprise-applications/ 2011/062311-security-summit.html
14. Jensen M, Schwenk J, Gruschka N, Iacono LL (2009) On Technical Security 44. Ristenpart T, Tromer E, Shacham H, Savage S (2009) Hey, you, get off of
Issues in Cloud Computing. In: IEEE Internation Conference on Cloud my cloud: exploring information leakage in third-party compute clouds.
Computing. pp 109–116 In: Proceedings of the 16th ACM conference on Computer and
15. TrendMicro (2010) Cloud Computing Security - Making Virtual Machines communications security, CCS ’09. New York, NY, USA, ACM, pp 199–212,
Cloud-Ready. Trend Micro White Paper doi.acm.org/10.1145/1653662.1653687
16. Genovese S (2009) Akamai Introduces Cloud-Based Firewall. http:// 45. Chow R, Golle P, Jakobsson M, Shi E, Staddon J, Masuoka R, Molina J
cloudcomputing.sys-con.com/node/1219023 (2009) Controlling data in the cloud: outsourcing computation without
17. Hulme GV (2011) CloudPassage aims to ease cloud server security outsourcing control. In: Proceedings of the 2009 ACM workshop on,
management. http://www.csoonline.com/article/658121/cloudpassage- Cloud computing security, CCSW ’09. New York, NY, USA, ACM, pp 85–90,
aims-to-ease-cloud-server-security-management http://doi.acm.org/10.1145/1655008.1655020
18. Oleshchuk VA, Køien GM (2011) Security and Privacy in the Cloud - A 46. Sadeghi AR, Schneider T, Winandy M (2010) Token-Based Cloud
Long-Term View. In: 2nd International Conference on Wireless Computing - Secure Outsourcing of Data and Arbitrary Computations
Communications, Vehicular Technology, Information Theory and with Lower Latency. In: Proceedings of the 3rd international conference
Aerospace and Electronic Systems Technology (Wireless VITAE), WIRELESS on Trust and trustworthy computing, TRUST ’10
VITAE ’11. pp 1–5, http://dx.doi.org/10.1109/WIRELESSVITAE.2011.5940876 47. Brandic I, Dustdar S, Anstett T, Schumm D, Leymann F (2010) Compliant
19. Google (2011) Google App Engine. code.google.com/appengine/ Cloud Computing (C3): Architecture and Language Support for
20. Google (2011) Google Query Language (GQL). User-driven Compliance Management in Clouds. In: 2010 IEEE 3rd
code.google.com/intl/en/appengine/docs/python/overview.html International Conference on Cloud Computing. pp 244–251, http://dx.
21. StackOverflow (2011) Does using non-SQL databases obviate the need doi.org/10.1109/CLOUD.2010.42
for guarding against SQL injection? 48. Brodkin J (2008) Gartner: Seven cloud computing security risks. http://
stackoverflow.com/questions/1823536/does-using-non-sql-databases- www.infoworld.com/d/security-central/gartner-seven-cloud-
obvia computing-security-risks-853
te-the-need-for-guarding-against-sql-injection 49. Kandukuri BR, Paturi R, Rakshit A (2009) Cloud Security Issues. In:
22. Rose J (2011) Cloudy with a chance of zero day. www.owasp.org/images/ Proceedings of the 2009 IEEE International Conference on Services
1/12/Cloudy with a chance of 0 day Jon Rose-Tom Leavey.pdf Computing, SCC ’09
23. Balkan A (2011) Why Google App Engine is broken and what Google 50. Winterford B (2011) Amazon EC2 suffers huge outage. http://www.crn.
must do to fix it. aralbalkan.com/1504 com.au/News/255586,amazon-ec2-suffers-huge-outage.aspx
24. Salesforce (2011) Salesforce Security Statement. 51. Clarke G (2011) Microsoft BPOS cloud outage burns Exchange converts.
salesforce.com/company/privacy/security.jsp http://www.theregister.co.uk/2011/05/13/
25. Espiner T (2007) Salesforce tight-lipped after phishing attack. 52. Shankland S (2011) Amazon cloud outage derails Reddit, Quora
zdnet.co.uk/news/security-threats/2007/11/07/salesforce-tight-lipped-a 53. Young E (2009) Cloud Computing - The role of internal audit
fter-phishing-attack-39290616/ 54. CloudAudit (2011) A6 - The automated audit, assertion, assessment and
26. Yee A (2007) Implications of Salesforce Phishing Incident. assurance API. http://cloudaudit.org/
ebizq.net/blogs/security insider/2007/11/-implications of salesforc 55. Anand N (2010) The legal issues around cloud computing. http://www.
e phi.php labnol.org/internet/cloud-computing-legal-issues/14120/
Gonzalez et al. Journal of Cloud Computing: Advances, Systems and Applications 2012, 1:11 Page 18 of 18
http://www.journalofcloudcomputing.com/content/1/1/11

56. Hunter S (2011) Ascending to the cloud creates negligible e-discovery

risk. http://ediscovery.quarles.com/2011/07/articles/information- doi:10.1186/2192-113X-1-11
technology/ascending-to-the-cloud-creates-negligible-ediscovery-risk/ Cite this article as: Gonzalez et al.: A quantitative analysis of current security
57. Sharon D, Nelson JWS (2011) Virtualization and Cloud Computing: concerns and solutions for cloud computing. Journal of Cloud Computing:
Advances, Systems and Applications 2012 1:11.
benefits and e-discovery implications. http://www.slaw.ca/2011/07/19/
virtualization-and-cloud-computing-benefits-and-e-discovery-
implications/
58. Bentley L (2009) E-discovery in the cloud presents promise and problems.
http://www.itbusinessedge.com/cm/community/features/interviews/
blog/e-discovery-in-the-cloud-presents-promise-and-problems/?cs=
31698
59. Zierick J (2011) The special case of privileged users in the sloud. http://
blog.beyondtrust.com/bid/63894/The-Special-Case-of-Privileged-Users-
in-the-Cloud
60. Dinoor S (2010) Got Privilege? Ten Steps to Securing a Cloud-Based
Enterprise. http://cloudcomputing.sys-con.com/node/1571649
61. Pavolotsky J (2010) Top five legal issues for the cloud. http://www.forbes.
com/2010/04/12/cloud-computing-enterprise-technology-cio-network-
legal.html
62. ENISA (2011) About ENISA. http://www.enisa.europa.eu/about-enisa
63. CSA (2011) About. https://cloudsecurityalliance.org/about/
64. CSA (2011) CSA TCI Reference Architecture. https://cloudsecurityalliance.
org/wp-content/uploads/2011/11/TCI-Reference-Architecture-1.1.pdf
65. CSA (2011) Security Guidance for Critical Areas of Focus in Cloud
Computing V3.0. Tech. rep., Cloud Security Alliance. [Http://www.
cloudsecurityalliance.org/guidance/csaguide.v3.0.pdf]
66. Ramireddy S, Chakraborthy R, Raghu TS, Rao HR (2010) Privacy and
Security Practices in the Arena of Cloud Computing - A Research in
Progress. In: AMCIS 2010 Proceedings, AMCIS ’10. http://aisel.aisnet.org/
amcis2010/574
67. NIST (2011) NIST Cloud Computing Reference Architecture: SP 500-292.
http://collaborate.nist.gov/twiki-cloud-computing/pub/
CloudComputing/ReferenceArchitectureTaxonomy/NIST SP 500-292 -
090611.pdf
68. Youseff L, Butrico M, Silva DD (2008) Toward a Unified Ontology of Cloud
Computing. In: Grid Computing Environments Workshop, 2008. GCE ’08.
pp 10, 1, http://dx.doi.org/10.1109/GCE.2008.4738443
69. Johnston S (2008) Sam Johnston: taxonomy: the 6 layer cloud computing
stack. http://samj.net/2008/09/taxonomy-6-layer-cloud-computing-
stack.html]
70. Linthicum D (2009) Defining the cloud computing framework. http://
cloudcomputing.sys-con.com/node/811519
71. Doelitzscher F, Reich C, Knahl M, Clarke N (2011) An autonomous agent
based incident detection system for cloud environments. In: Third IEEE
International Conference on Cloud Computing Technology and Science,
CloudCom 2011, CPS. pp 197–204, http://dx.doi.org/10.1109/CloudCom.
2011.35
72. Oltsik J (2010) Information security, virtualization, and the journey to the
cloud. Tech. rep., Cloud Security Alliance
73. Wallom D, Turilli M, Taylor G, Hargreaves N, Martin A, Raun A, McMoran A
(2011) myTrustedCloud: Trusted Cloud Infrastructure for Security-critical
Computation and Data Managment. In: Third IEEE International
Conference on Cloud Computing Technology and Science, CloudCom
2011, CPS. pp 247–254
74. Dabrowski C, Mills K (2011) VM Leakage and Orphan Control in
Open-Source Clouds. In: Third IEEE International Conference on Cloud
Computing Technology and Science, CloudCom 2011, CPS. pp 554–559
75. Chadwick DW, Casenove M (2011) Security APIs for My Private Cloud. In:
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