Backdoor.PS1.AXIOSRAT.THCCABF

This Backdoor arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It executes commands from a remote malicious user, effectively compromising the affected system.

It steals certain information from the system and/or the user.

Arrival Details

This Backdoor arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

Installation

This Backdoor drops the following files:

• %ProgramData%\system.bat → sends string to C2 server then downloads and executes C2 response
• %User Temp%\[random].ps1 → script from the C2 server

(Note: %ProgramData% is a version of the Program Files folder where any user on a multi-user computer can make changes to programs. This contains application data for all users. This is usually C:\ProgramData on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit), or C:\Documents and Settings\All Users on Windows Server 2003(32-bit), 2000(32-bit) and XP.. %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Local\Temp on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).)

Autostart Technique

This Backdoor adds the following registry entries to enable its automatic execution at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
MicrosoftUpdate = %ProgramData%\system.bat

Backdoor Routine

This Backdoor executes the following commands from a remote malicious user:

• kill → self-destruct
• peinject → injects payload in cmd.exe
• runscript → runs script from c2
• rundir → run a remote file browser

Information Theft

This Backdoor steals the following information:

• Username
• Computer name
• Timezone information
• Boot time
• OS Installation date
• OS Version
• Hardware model
• CPU model
• Directory Listing of specific locations
• Running processes

Other Details

This Backdoor does the following:

• It gets the C2 server from the execution argument.
• It gets directory listing of the following folder:
  • [drive roots]
  • %User Profile%\Documents
  • %User Profile%\Desktop
  • %User Profile%\OneDrive
  • %User Profile%\AppData\Roaming
• It adds hidden attribute to the following file:
  • %ProgramData%\system.bat

(Note: %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name} on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).. %ProgramData% is a version of the Program Files folder where any user on a multi-user computer can make changes to programs. This contains application data for all users. This is usually C:\ProgramData on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit), or C:\Documents and Settings\All Users on Windows Server 2003(32-bit), 2000(32-bit) and XP.)