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BKDR_OFICLA.WGH

October 08, 2012
 Analysis by: Michael Cabel
 PLATFORM:

Windows 2000, XP, Server 2003

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

This backdoor opens a random port to allow a remote user to connect to the affected system. Once a successful connection is established, the remote user executes commands on the affected system.

  TECHNICAL DETAILS

File Size:

22,016 bytes

File Type:

DLL

Memory Resident:

Yes

Initial Samples Received Date:

10 Nov 2010

Installation

This backdoor drops the following copies of itself into the affected system:

  • %System%\{Random File Name}

(Note: %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.)

Autostart Technique

This backdoor modifies the following registry entries to ensure it automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
Shell = "Explorer.exe rundll32.exe {Malware File Name} tmilnrm"

(Note: The default value data of the said registry entry is "Explorer.exe".)

Backdoor Routine

This backdoor opens a random port to allow a remote user to connect to the affected system. Once a successful connection is established, the remote user executes commands on the affected system.

It connects to the following URL(s) to send and receive commands from a remote malicious user:

  • {BLOCKED}imeru.ru

  SOLUTION

Minimum Scan Engine:

8.900

FIRST VSAPI PATTERN FILE:

07.610.02

FIRST VSAPI PATTERN DATE:

10 Nov 2010

Step 1

For Windows XP and Windows Server 2003 users, before doing any scans, please make sure you disable System Restore to allow full scanning of your computer.

Step 2

Scan your computer with your Trend Micro product and note files detected as BKDR_OFICLA.WGH

Step 3

Restart in Safe Mode

[ Learn More ]

Step 4

Restore this modified registry value

[ Learn More ]

Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.

 
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
    • From: Shell = Explorer.exe rundll32.exe {Malware File Name} tmilnrm
      To: Explorer.exe

Step 5

Search and delete the file detected as BKDR_OFICLA.WGH

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden files in the search result.


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