Windows environment variables are one such critical component that forensic analysts must be familiar with. These variables function like shortcuts to specific system locations, and they play a pivotal role in both legitimate and malicious activities.
What are Environment Variables?
Environment variables in Windows are dynamic values that the operating system and applications use to determine various settings and locations on the computer. These variables are often used to point to directories, system paths, and configuration settings. They can be predefined by the operating system or created by users and administrators.
Common Windows Environment Variables
Here are some commonly used environment variables and their typical paths:
%APPDATA%: Points to the current user's Roaming profile directory.
Example: C:\Users\noransom\AppData\Roaming
This directory is used for storing application data that should roam with the user profile across different machines.
%LOCALAPPDATA%: Points to the current user's Local profile directory.
Example: C:\Users\noransom\AppData\Local
Data in this directory stays local to the machine and does not roam.
%TEMP%: Points to the temporary files directory.
Example: C:\Users\noransom\AppData\Local\Temp
This is where temporary files are stored and is often targeted by malware for temporary storage.
%ComSpec%: Points to the command prompt executable.
Example: C:\Windows\system32\cmd.exe
%ProgramData%: Points to the application data folder that is shared among all users.
Example: C:\ProgramData
Why Environment Variables Matter in Forensics
Environment variables are crucial in forensic investigations for several reasons:
Tracing User Activity: By examining the paths pointed to by environment variables, forensic analysts can trace the activities of users on the system. For example, the %APPDATA% directory can contain configuration files and logs of applications that provide insights into user actions.
Identifying Malicious Behavior: Attackers often exploit environment variables to obfuscate their activities. They might create custom variables to hide malicious files or chain multiple variables to execute commands without leaving obvious traces.
Streamlining Analysis: Knowing how to reference environment variables can streamline the forensic analysis process. Analysts can quickly navigate to relevant directories and files by using these shortcuts.
How Attackers Exploit Environment Variables
Attackers frequently use environment variables to their advantage in several ways:
Persistence Mechanisms: Malware often stores configuration files and executables in directories referenced by environment variables like %APPDATA% or %TEMP%, ensuring they persist across reboots.
Command Obfuscation: By creating and chaining environment variables, attackers can obfuscate their commands. For example, an attacker might create a variable %MALWARE% pointing to their payload and then execute it by referencing %MALWARE%.
Evasion Techniques: Using environment variables can help malware evade detection by traditional file path-based security mechanisms.
Listing Environment Variables
To view all environment variables accessible by your current account, you can use the following commands:
Command Prompt: set
PowerShell: ls env:
Practical Example
Let's say an attacker has placed a malicious script in the %APPDATA% directory and is using an environment variable to run it. You can quickly check what the %APPDATA% variable points to by running:
echo %APPDATA%This command will display the full path, helping you navigate to the directory and investigate further.
Conclusion
These variables provide valuable insights into user activities and are often manipulated by attackers to obfuscate their actions. By familiarizing yourself with common environment variables and how they are used, you can enhance your ability to detect, analyze, and respond to security incidents effectively.
Akash Patel
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