Analysis by: Sabrina Lei Sioting
 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

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 deletes the initially executed copy of itself.

  TECHNICAL DETAILS

File Size: 38,912 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 08 Oct 2011

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:

  • %System%\csrsc.exe

(Note: %System% is the Windows system folder, which is usually C:\Windows\System32.)

Autostart Technique

This backdoor registers itself as a system service to ensure its automatic execution at every system startup by adding the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Enum\Root\LEGACY_WINSPOOLSVC\
0000
Service = "WinSpoolSvc"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\WinSpoolSvc
ImagePath = "%System%\csrsc.exe"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\WinSpoolSvc
DisplayName = "Windows Spool Services"

Other System Modifications

This backdoor adds the following registry keys:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Enum\Root\LEGACY_WINSPOOLSVC

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\WinSpoolSvc

Other Details

This backdoor deletes the initially executed copy of itself