PE_KOLOBOK.A-O

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

It prepends its codes to target files. It infects certain file types by inserting code in the said files. It creates an infection marker in infected files.

It does not have any propagation routine.

It does not have any backdoor routine.

This is the Trend Micro detection for files that exhibit certain behaviors.

Arrival Details

This file infector 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 file infector drops a copy of itself in the following folders using different file names:

• %Application Data%\wecox.~p1 <- modified copy, prepended with “??KOLO” before the MZ header

(Note: %Application Data% is the Application Data folder, where it usually is C:\Documents and Settings\{user name}\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)

It drops the following copies of itself into the affected system and executes them:

• %Application Data%\services.exe <- with “-?cwk” as argument
• %Application Data%\wecox.~p0

(Note: %Application Data% is the Application Data folder, where it usually is C:\Documents and Settings\{user name}\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)

It adds the following mutexes to ensure that only one of its copies runs at any one time:

• PACMAN:CLOCKWORK:KOLOBOK

File Infection

This file infector prepends its codes to target files.

It infects files with the following file extensions by inserting code in the said files:

• .exe
• .scr
• .zip
• .rar
  (Note: The affected system must have a WinRAR installed for infection to .rar and .zip to work)
  It infects .rar and .zip file by dropping an infected copy of “msiexec.exe” to the archives
  • Uses the following shell command to aid this routine:
    • %Program Files%\WinRAR\WinRAR.exe a –ep –ibck –m5 –u –y – %User Temp%\{list of file names}{random number}.exe

(Note: %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)

It creates an infection marker in infected files.

It avoids infecting folders containing the following strings:

• "ram f" <- Program Files
• ":\win" <- Windows Directory
• "\sys" <- System Directory
• "\recy" <- Recycle Bin
• TEMP <- Temp Folder
• APPDATA <- Application Data

Propagation

This file infector does not have any propagation routine.

Backdoor Routine

This file infector does not have any backdoor routine.

Dropping Routine

This file infector drops the following files:

• %User Temp%\{random}.{random} <- temporary copy of target file to infect, deleted afterwards
• %User Temp%\{list of file names}{random number}.exe <- temporary copy of infected “msiexec.exe”, deleted afterwards
  Where {list of file names} can be any of the following:
  • install
  • upgrade
  • trainer
  • license
  • keygen
  • serial
  • setup
  • patch
  • crack
  • cheat
  • cdkey

(Note: %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)

Other Details

This is the Trend Micro detection for:

• The mother file for PE_KOLOBOK.A

It does the following:

• Uses the following as infection marker:
  • NAMCAP
  • Size of malicious code after NAMCAP
• It infects the following drive types:
  • Fixed
    • Only infects when the directory is currently open in explorer
    • The malware hooks the explorer.exe to check for open directories to infect
  • Removable
  • Remote
    • Infects remote or removable drives when (TickCount from first execution – TickCount from last event/action) > 1500000 ms (~25 mins)

NOTES:

It does not have rootkit capabilities.

It does not exploit any vulnerability.