Analysis by: Rika Joi Gregorio
ALIASES:

Backdoor:Win32/Fynloski.A(Microsoft), Trojan.Klovbot(Norton), PWS-Zbot.gen.arw(McAfee), W32/DarkKomet.AEOY!tr.bdr(Fortinet)

 PLATFORM:

Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)

 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.

  TECHNICAL DETAILS

File Size: 720,896 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 15 Mar 2013

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 adds the following folders:

  • %User Temp%\MSDCSC

(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 and 7.)

It drops the following copies of itself into the affected system:

  • %User Temp%\MSDCSC\msdcsc.exe

(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 and 7.)

Autostart Technique

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

HKEY_CURRENT_USER\Microsoft\Windows\
CurrentVersion\Run
MicroUpdate = "%User Temp%\MSDCSC\msdcsc.exe"

Other System Modifications

This backdoor adds the following registry keys:

HKEY_CURRENT_USER\Software\DC3_FEXEC

Other Details

This backdoor connects to the following possibly malicious URL:

  • jmark4040.{BLOCKED}p.biz