BKDR_PROTUX.SMZKEB-G

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 then deletes itself afterward.

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

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 copies of itself into the affected system:

• %User Temp%\{malware name}.exe
• %Windows%\LINKINFO.dll
• %User Temp%\cnagnt.dll
• %User Temp%\ppa{Random hex value}.tmp → temporary DLL
• %User Temp%\RCX{Random hex value}.tmp → temporary DLL
• %Application Data%\cnagnt.dll

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista, 7, and 8.. %Windows% is the Windows folder, where it usually is C:\Windows on all Windows operating system versions.. %Application Data% is the current user's Application Data folder, which is usually C:\Documents and Settings\{user name}\Application Data on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Roaming on Windows Vista, 7, and 8.)

It drops the following files:

• %User Temp%\1.txt → Contains the malware's process information. Deleted afterwards.
• %User Temp%\ppa{Random hex value}.tmp.vbs
• {Malware path}\q.bat → Uninstall itself. Deleted afterwards.

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista, 7, and 8.)

It executes then deletes itself afterward.

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

• tmutexabc

Autostart Technique

This Backdoor creates the following registry entries to enable automatic execution of dropped component at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Conime = "%System%\rundll32" "%User Temp%\ppa{Random hex value}.tmp",Sd

It drops the following file(s) in the Windows Startup folder to enable its automatic execution at every system startup:

• %User Startup%\Conime.lnk
• %User Startup%\Conime.exe

(Note: %User Startup% is the current user's Startup folder, which is usually C:\Windows\Profiles\{user name}\Start Menu\Programs\Startup on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Start Menu\Programs\Startup on Windows NT, C:\Documents and Settings\{User name}\Start Menu\Programs\Startup on Windows XP, or C:\Users\{user name}\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup on Windows Vista, 7, and 8.)

Other System Modifications

This Backdoor adds the following registry entries:

HKEY_CURRENT_USER\Control Panel\Desktop
WaitToKillAppTimeout = 1000

Backdoor Routine

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

• Upload victim information.
• Execute a batch script, executable file or DLL file.

Other Details

This Backdoor connects to the following URL(s) to check for an Internet connection:

• http://www.bing.com/

It does the following:

• It checks for the existence of the following AV products:
  
  • norton
  • synmantec
  • trend micro
  • kaspersky
  • avira
  • avg
• It checks for the existence of the following AV related processes:
  
  • uiseagnt.exe
  • v3ltray.exe
  • ayagent.aye
  • avp.exe
  • avgnt.exe
  • ccsvchst.exe
  • pccntmon.exe
  • cntaosmgr.exe
  • klnagent.exe
  • avg
• If any of the AV related product is found:
  
  • Convert itself to a temporary DLL with a default export of ‘Dm’ in the %User Temp% directory.
  • If running with administrator privileges on a 32-bit system:
    
    • Copy the temporary DLL in %User Temp% to %Windows%\LINKINFO.dll
  • If not,
    
    • If its file name has "emp\low" in it. The malware copies the temporary DLL to %User Temp%\cnagnt.dll
    • Else, the malware copies the temporary DLL to %Application Data%\cnagnt.dll
    • Delete the temporary DLL in %User Temp%
    • Create %User Startup%\Conime.lnk that points to either
      
      • %System%\rundll32.exe "%Application Data%\cnagnt.dll",Sd
      • %System%\rundll32.exe "%User Temp%\cnagnt.dll",Sd
• It connects to the following URL to download data that contains the command and control server(s) and port(s):
  
  • https://github.com/{BLOCKED}ff
  • http://{BLOCKED}see.tumblr.com:443
  
  However, as of this writing the said sites are inaccessible.
• It adds garbage data to its copies to avoid easy detection.
• Checks if it is running in %User Temp%. If not, it will copy itself to %User Temp% and execute the copy with the following command:
  
  • "%User Temp%\{malware name}.exe" {Malware path}\{Malware name}.exe