Chapter 7

Security Technology:
Intrusion Detection and
Prevention Systems, and
Other Security Tools
 Learning Objectives
• Upon completion of this material, you should be able to:

― Identify and describe the categories and models of intrusion

detection and prevention systems.

― Describe the detection approaches employed by modern

intrusion detection and prevention systems.

― Define and describe honeypots, honeynets, and padded cell

systems.

― List and define the major categories of scanning and analysis

tools, and describe the specific tools used within each category.
 Introduction
• Protection of organizations assets relies as
much on managerial controls as on technical
safeguards.
• Properly implemented technical solutions
guided by policy are essential to an information
security program.
• Advanced technologies can be used to enhance
the security of information assets.
 Intrusion Detection and Prevention
Systems
• An intrusion is a type of attack on information assets in
which an attacker attempts to gain entry into or disrupt the
normal operations of an organization’s information systems.
• An intrusion prevention system (IPS)consists of activities
that seek to deter an intrusion from occurring .
• An intrusion detection system (IDS)consists of procedures
and systems that are created and operated to detect system
intrusions.
• The term intrusion detection/prevention system (IDPS)can
be used to describe current anti-intrusion technologies.
 Intrusion Detection and Prevention
Systems(cont’d)
• Intrusion correction activities: complete restoration of
operations to a normal state and seek to identify
source and method of intrusion.
• Intrusion detection systems detect a violation of its
configuration and activate alarm.
• Many IDPSs enable administrators to configure systems
to notify them directly of trouble via e-mail or pagers.
• Systems can also be configured to notify an external
security service organization of a “break in.”
 Why Use an IDPS?
• Intrusion detection:
– Primary purpose to identify and report an intrusion
– Can quickly contain attack and prevent/mitigate loss or damage
– Detect and deal with preambles to attacks
• Data collection allows the organization to examine what
happened after an intrusion and why.
• Serves as a deterrent by increasing the fear of detection
• Can help management with quality assurance and
continuous improvement.
 Types of IDPSs

• IDPSs operate as network-based or host-

based systems:
1) Network-based IDPS (NIDPS) is focused on
protecting network information assets.
– Wireless IDPS: focuses on wireless networks.
– Network behavior analysis IDPS: examines
traffic flow on a network in an attempt to
recognize abnormal patterns.
Types of IDPSs
 Types of IDPSs

• Advantages of NIDPSs
 Good network design and placement of NIDPS can
enable an organization to monitor a large network
with few devices.
 NIDPSs are usually passive and can be deployed into
existing networks with little disruption to normal
network operations.
 NIDPSs are not usually susceptible to direct attack and
may not be detectable by attackers.
 Types of IDPSs

• Disadvantages of NIDPSs
 Can become overwhelmed by network volume and
fail to recognize attacks.
 Require access to all traffic to be monitored.
 Cannot analyze encrypted packets.
 Cannot reliably ascertain if attack was successful or
not.
 Some forms of attack are not easily discerned by
NIDPSs, specifically those involving fragmented
packets.
 Types of IDPSs
2) Host-based IDPS (HIDPS)
 Resides on a particular computer or server (host) and
monitors activity only on that system.
 Benchmarks and monitors the status of key system files
and detects when intruder creates, modifies, or deletes
files.
 Advantage over NIDPS: can access encrypted information
traveling over network and make decisions about
potential/actual attacks.
 Most HIDPSs work on the principle of configuration or
change management.
 Types of IDPSs
Advantages of HIDPSs
 Can detect local events on host systems and detect
attacks that may elude a network-based IDPS.
 Functions on host system, where encrypted traffic will
have been decrypted and is available for processing.
 Not affected by use of switched network protocols.
 Can detect inconsistencies in how applications and
systems programs were used by examining records
stored in audit logs.
 Types of IDPSs
Disadvantages of HIDPSs
 Pose more management issues.
 Vulnerable both to direct attacks and attacks against host
operating system.
 Does not detect multihost scanning, nor scanning of
non-host network devices.
 Susceptible to some DoS attacks.
 Can use large amounts of disk space.
 Can inflict a performance overhead on its host systems.
 IDPS Detection Methods
Signature-based detection
• Examines network traffic in search of patterns that
match known signatures.
• Widely used because many attacks have clear and
distinct signatures.
• Problem with this approach is that new attack patterns
must continually be added to IDPS’s database of
signatures.
– Slow, methodical attack involving multiple events might escape
detection.
 IDPS Detection Methods(cont’d)
Anomaly-based detection
• Anomaly-based detection (or behavior-based detection)
collects statistical summaries by observing traffic known
to be normal.
• When measured activity is outside baseline parameters
or clipping level, IDPS sends alert to administrator.
• IDPS can detect new types of attacks.
• Requires much more overhead and processing capacity
than signature-based detection.
• May generate many false positives.
 IDPS Detection Methods(cont’d)
Stateful protocol analysis
• SPA: process of comparing known normal/benign
protocol profiles against observed traffic.
• Stores and uses relevant data detected in a session to
identify intrusions involving multiple requests
/responses; allows IDPS to better detect specialized,
multisession attacks (also called deep packet inspection)
• Drawbacks: analytical complexity; heavy processing
overhead; may fail to detect intrusion unless protocol
violates fundamental behavior.
 IDPS Detection Methods(cont’d)
Log file monitors
• Log file monitor (LFM) similar to NIDPS.
• Reviews log files generated by servers, network devices,
and even other IDPSs for patterns and signatures.
• Patterns that signify attack may be much easier to
identify when entire network and its systems are viewed
as a whole.
• Requires considerable resources since it involves the
collection, movement, storage, and analysis of large
quantities of log data.
 Strengths and Limitations of IDPSs
• IDPSs perform the following functions well:
– Monitoring and analysis of system events and user
behaviors.
– Testing security states of system configurations.
– Baselining security state of system and tracking
changes.
– Recognizing patterns of system events corresponding
to known attacks.
– Recognizing activity patterns that vary from normal
activity.
 Strengths and Limitations of IDPSs
(cont’d)
• IDPSs perform the following functions well:
– Managing OS audit and logging mechanisms and data
they generate.
–Alerting appropriate staff when attacks are detected.
– Measuring enforcement of security policies encoded in
analysis engine.
– Providing default information on security policies.
– Allowing non-security experts to perform important
security monitoring functions.
 Strengths and Limitations of IDPSs
(cont’d)
• IDPSs cannot perform the following functions:
–Compensating for weak/missing security mechanisms
in protection infrastructure.
–Instantaneously detecting, reporting, responding to
attack when there is heavy network or processing load.
–Detecting new attacks or variants of existing attacks.
–Effectively responding to attacks by sophisticated
attackers.
–Automatically investigating attacks without human
intervention.
 Strengths and Limitations of IDPSs
(cont’d)
• IDPSs cannot perform the following functions:
– Resisting attacks intended to defeat or circumvent
them.
– Compensating for problems with fidelity of
information sources.
– Dealing effectively with switched networks.
 Implementation of an IDPS
• An IDPS can be implemented via one of three
basic control strategies:
–Centralized: All IDPS control functions are implemented
and managed in a central location.
–Fully distributed: All control functions are applied at
the physical location of each IDPS component.
–Partially distributed: Combines the two; while
individual agents can still analyze and respond to local
threats, they report to a hierarchical central facility to
enable organization to detect widespread attacks.
Implementation of an IDPS

Centralized IDPS Control

Implementation of an IDPS

Fully Distributed IDPS Control

Implementation of an IDPS

Partially Distributed IDPS Control

 Honeypots, Honeynets, and Padded Cell
Systems
• Honeypots: decoy systems designed to lure
potential attackers away from critical systems
• Honeynets: several honeypots connected together
on a network segment
• Honeypots are designed to:
–Divert attacker from accessing critical systems
–Collect information about attacker’s activity
–Encourage attacker to stay on a system long enough for
administrators to document the event and perhaps
respond
Honeypots, Honeynets, and Padded Cell Systems
(cont’d)
• Padded cell system: protected honeypot that
cannot be easily compromised.
• In addition to attracting attackers with tempting
data, a padded cell operates in tandem with a
traditional IDPS.
• When the IDPS detects attackers, padded cell
system seamlessly transfers them to a special
simulated environment where they can cause no
harm—hence the name padded cell.
Honeypots, Honeynets, and Padded Cell Systems
(cont’d)
• Advantages
–Attackers can be diverted to targets they cannot
damage.
–Administrators have time to decide how to respond to
an attacker.
–Attackers’ actions can be easily and more extensively
monitored, and records can be used to refine threat
models and improve system protections.
–Honeypots may be effective at catching insiders who
are snooping around a network.
Honeypots, Honeynets, and Padded Cell Systems
(cont’d)
• Disadvantages
–Legal implications of using such devices are not well
understood.
–Honeypots and padded cells have not yet been shown
to be generally useful security technologies.
–An expert attacker, once diverted into a decoy system,
may become angry and launch a more aggressive attack
against an organization’s systems.
–Administrators and security managers need a high level
of expertise to use these systems.
 Scanning and Analysis Tools
• Scanning tools typically are used to collect
information that an attacker needs to launch a
successful attack.

• Attack protocol is a logical sequence of steps or

processes used by an attacker to launch an attack
against a target system or network.

• Footprinting: process of collecting publicly

available information about a potential target .
 Scanning and Analysis Tools
• Fingerprinting: systematic survey of target organization’s
Internet addresses collected during the footprinting
phase to identify network services offered by hosts in
that range.
• Fingerprinting reveals useful information about the
internal structure and nature of the target system or
network to be attacked.
• These tools are valuable to the network defender since
they can quickly pinpoint the parts of the systems or
network that need a prompt repair to close
vulnerabilities.
 Port Scanners

• Tools used by both attackers and defenders to

identify/fingerprint computers active on a
network and other useful information.
• Can either perform generic scans or those for
specific types of computers, protocols, or
resources.
• The more specific the scanner is, the more useful
its information is to attackers and defenders.
Port Scanners
 Vulnerability Scanners
•
• Active vulnerability scanners examine networks
for highly detailed information and initiate traffic
to determine security holes.
• Passive vulnerability scanners listen in on network
and identify the vulnerable versions of both
server and client software.
• Passive vulnerability scanners have the ability to
find client-side vulnerabilities typically not found
in active scanners.
 Vulnerability Scanners
•
• Network tool that captures copies of packets from network and
analyzes them.

• Can provide network administrator with valuable information

for diagnosing and resolving networking issues.

• A packet sniffer — also known as a packet analyzer, protocol

analyzer or network analyzer — is a piece of hardware or
software used to monitor network traffic. Sniffers work by
examining streams of data packets that flow between
computers on a network as well as between networked
computers and the larger Internet.
 Summary
• Intrusion detection system (IDPS) detects
violation of its configuration and activates alarm.
• Network-based IDPS (NIDPS) versus host-based
IDPS (HIDPS).
• Selecting IDPS products that best fit an
organization’s needs is challenging and complex.
• Honeypots are decoy systems; two variations are
known as honeynets and padded cell systems.
 Summary (cont’d)
• Scanning and analysis tools are used to pinpoint
vulnerabilities in systems, holes in security
components, and unsecured aspects of a
network.