Practical Malware
Analysis
Ch 2: Malware Analysis in Virtual
Machines
Updated 2-2-21
Dynamic Analysis
• Running malware deliberately, while
monitoring the results
• Requires a safe environment
• Must prevent malware from spreading to
production machines
• Real machines can be airgapped –no
network connection to the Internet or to
other machines
Real Machines
• Disadvantages
– No Internet connection, so parts of the
malware may not work
– Can be difficult to remove malware, so re-
imaging the machine will be necessary
• Advantage
– Some malware detects virtual machines and
won't run properly in one
Virtual Machines
• The most common method
• We'll do it that way
• This protects the host machine from the
malware
– Except for a few very rare cases of malware
that escape the virtual machine and infect
the host
VMware Workstation Player/Fusion
• Free for education
• Cannot take snapshots
• You could also use VirtualBox, Hyper-V,
Parallels, or Xen.
Configuring VMware
• You can disable networking by
disconnecting the virtual network adapter
• Host-only networking allows network
traffic to the host but not the Internet
Connecting Malware to the Internet
• NAT mode lets VMs see each other and the
Internet, but puts a virtual router
between the VM and the LAN
• Bridged networking connects the VM
directly to the LAN
• Can allow malware to do some harm or
spread – controversial
• You could send spam or participate in a
DDoS attack
Snapshots
Risks of Using VMware for Malware
Analysis
• Malware may detect that it is in a VM and
run differently
• VMware has bugs: malware may crash or
exploit it
• Malware may spread or affect the host –
don't use a sensitive host machine
• All the textbook samples are harmless
Practical Malware Analysis
Ch 3: Basic Dynamic Analysis
Why Perform Dynamic Analysis?
• Static analysis can reach a dead-end, due
to
– Obfuscation
– Packing
– Examiner has exhausted the available static
analysis techniques
• Dynamic analysis is efficient and will show
you exactly what the malware does
Sandboxes: The Quick-and-
Dirty Approach
Sandbox
• All-in-one software for basic dynamic
analysis
• Virtualized environment that simulates
network services
• Examples: Norman Sandbox, GFI Sandbox,
Anubis, Joe Sandbox, ThreatExpert,
BitBlaze, Comodo Instant Malware Analysis
• They are expensive but easy to use
• They produce a nice PDF report of results
Running Malware
Launching DLLs
• EXE files can be run directly, but DLLs
can't
• Use Rundll32.exe (included in Windows)
rundll32.exe DLLname, Export arguments
• The Export value is one of the exported
functions you found in Dependency
Walker, PEview, or PE Explorer.
Launching DLLs
• Example
– rip.dll has these exports: Install and Uninstall
rundll32.exe rip.dll, Install
• Some functions use ordinal values instead
of names, like
rundll32.exe xyzzy.dll, #5
• It's also possible to modify the PE header
and convert a DLL into an EXE
Monitoring with Process
Monitor
Process Monitor
• Monitors registry, file system, network,
process, and thread activity
• All recorded events are kept, but you can
filter the display to make it easier to find
items of interest
• Don't run it too long or it will fill up all
RAM and crash the machine
Launching Calc.exe
• Many, many events recorded
Process Monitor Toolbar
Default Filters
Start/Stop Erase Filter Registry, File system, Network,
Capture Processes
Filtering with Exclude
• One technique: hide normal activity
before launching malware
• Right-click each Process Name and click
Exclude
• Doesn't seem to work well with these
samples
Filtering with Include
• Most useful filters: Process Name,
Operation, and Detail
Viewing Processes with
Process Explorer
Coloring
• Services are pink
• Processes are blue
• New processes are green briefly
• Terminated processes are red
DLL Mode
Properties
• Shows DEP (Data
Execution Prevention)
and ASLR (Address
Space Layout
Randomization) status
• Verify button checks
the disk file's
Windows signature
– But not the RAM
image, so it won't
detect process
replacement
Strings
Compare Image
to Memory
strings, if they
are very
different, it can
indicate process
replacement
Detecting Malicious Documents
• Open the document (e.g. PDF) on a
system with a vulnerable application
• Watch Process Explorer to see if it
launches a process
• The Image tab of that process's Properties
sheet will show where the malware is
Comparing Registry Snapshots
with Regshot
Regshot
• Take 1st shot
• Run malware
• Take 2nd shot
• Compare them to
see what registry
keys were changed
Faking a Network
INetSim
• Included in Kali Linux
• Simulates the Internet, including
• HTTP / HTTPS
• SMTP, POP3
• DNS
• FTP
• Much more
Ncat Listener
• Using Ncat.exe, you can listen on a single
TCP port in Windows
• In Linux, use nc (netcat)
• This will allow malware to complete a TCP
handshake, so you get some rudimentary
information about its requests
• But it's not a real server, so it won't reply
to requests after the handshake
Monitoring with Ncat
(included with Nmap)
Packet Sniffing with Wireshark
Follow TCP Stream
• Can save
files
from
streams
here too
Using INetSim
inetsim
INetSim Fools a Browser
INetSim
Fools
Nmap
Basic Dynamic Tools in
Practice
Using the Tools
• Procmon
– Filter on the malware executable name and
clear all events just before running it
• Process Explorer
• Regshot
• Virtual Network with INetSim
• Wireshark
