Threat Hunting for Windows Shell Escape Characters in cmd.exe Execution

This threat hunting package aims to detect command obfuscation attempts within the Windows environment. Specifically, it focuses on identifying instances where shell escape characters are used in cmd.exe execution, which can indicate attempts to bypass security mechanisms and execute malicious commands with obfuscated payloads.

MITRE ATT&CK Tactics and Techniques:
Tactics: Execution, Defense Evasion
Techniques: T1059 Command and Scripting Interpreter (Windows Command Shell — cmd.exe)
T1140 Deobfuscate/Decode Files or Information (Obfuscation of commands)

The threat involves malicious actors attempting to obfuscate their commands during cmd.exe execution on a Windows system. By using shell escape characters, attackers aim to hide the true nature of their commands from security monitoring tools and defenders. These escape characters modify the interpretation of special characters, making it challenging for security solutions to detect and analyze the actual commands being executed. The obfuscation technique is commonly used by attackers to evade detection and execute malicious payloads.

Mitigation Recommendations:
- Implement robust application whitelisting to prevent unauthorized execution of commands and scripts.
- Regularly update and patch the Windows operating system to ensure the latest security fixes are applied.
- Educate users about the dangers of running commands or scripts from untrusted sources.
- Utilize advanced endpoint security solutions that can detect and block obfuscated command execution attempts.

Below are some Splunk queries that can be used for threat hunting related to command obfuscation attempts using shell escape characters in cmd.exe execution:

Detect Shell Escape Characters in cmd.exe Execution:

index=your_index sourcetype=your_sourcetype “cmd.exe”
(“ ^ “ OR “ & “ OR “ | “ OR “ < “ OR “ > “ OR “ ` “ OR “ ; “ OR “ * “)
| stats count by host, user, CommandLine
| sort — count

Identify Suspicious Child Processes from cmd.exe:

index=your_index sourcetype=your_sourcetype
(“cmd.exe” OR “powershell.exe” OR “wscript.exe” OR “cscript.exe”)
| eval isSuspicious=if(match(CommandLine, “ ^ | & | | | < | > | ` | ; | * “), “Yes”, “No”)
| where isSuspicious=”Yes”
| stats count by host, user, parent_process_name, CommandLine
| sort — count

Look for Uncommon Command Obfuscation Techniques:

index=your_index sourcetype=your_sourcetype
(“cmd.exe” OR “powershell.exe” OR “wscript.exe” OR “cscript.exe”)
| eval obfuscated=if(match(CommandLine, “ ^ | & | | | < | > | ` | ; | * “), “Yes”, “No”)
| where obfuscated=”Yes”
| stats count by host, user, parent_process_name, CommandLine
| sort — count

Note: Adjust the `your_index` and `your_sourcetype` with the appropriate values from your Splunk environment.

It is important to customize and fine-tune these queries based on your organization’s environment and specific use cases. Additionally, continuous monitoring and collaboration with security analysts and incident responders are essential for effective threat hunting and mitigation of command obfuscation attempts.

References:
- MITRE ATT&CK: https://attack.mitre.org/techniques/T1059/
- MITRE ATT&CK: https://attack.mitre.org/techniques/T1140/