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BKDR_FARFLI.DAA

October 09, 2012
 Analysis by: Kathleen Notario
 ALIASES:

Trojan.Gen (Symantec); Backdoor:Win32/Farfli.O (Microsoft); BackDoor-DVB (Mcafee); Troj/Farfli-Gen (Sophos)

 PLATFORM:

Windows 2000, Windows XP, Windows 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 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:

12,473,344 bytes

File Type:

DLL

Memory Resident:

No

Initial Samples Received Date:

31 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:

  • %Program Files%\Common Files\Acucpbjdn.jpg

(Note: %Program Files% is the default Program Files folder, usually C:\Program Files.)

It drops the following non-malicious file:

  • C:\Net-Temp.ini

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\
Services\Ebqfei Erogvuim Iet\Parameters
ServiceDll = %Program Files%\Common Files\Acucpbjdn.jpg

Other System Modifications

This backdoor adds the following registry keys as part of its installation routine:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Ebqfei Erogvuim Iet

HKEY_LOCAL_MACHINE\SOFTWARE\{random numbers}

HKEY_CURRENT_USER\NetSubKey

HKEY_USERS\.DEFAULT\NetSubKey

It modifies the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\SvcHost
imgsvc = {user defined} Ebqfei Erogvuim Iet

(Note: The default value data of the said registry entry is {user defined}.)

Backdoor Routine

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

  • {BLOCKED}ddos.3322.org

Other Details

This backdoor connects to the following possibly malicious URL:

  • http://www.{BLOCKED}u.com/ip.txt
  • http://www.{BLOCKED}aibinzang.com/zc2.htm

  SOLUTION

Minimum Scan Engine:

9.200

FIRST VSAPI PATTERN FILE:

8.538.01

FIRST VSAPI PATTERN DATE:

31 Oct 2011

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

Restart in Safe Mode

[ Learn More ]

Step 3

Delete this registry key

[ 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. Before you could do this, you must restart in Safe Mode. For instructions on how to do this, you may refer to this page If the preceding step requires you to restart in safe mode, you may proceed to edit the system registry.

  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services
    • Ebqfei Erogvuim Iet
  • In HKEY_LOCAL_MACHINE\SOFTWARE
    • {random numbers}
  • In HKEY_CURRENT_USER
    • NetSubKey
  • In HKEY_USERS\.DEFAULT
    • NetSubKey

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\SvcHost
    • From: imgsvc = {user defined} Ebqfei Erogvuim Iet
      To: imgsvc = {user defined}

Step 5

Search and delete this file

[ Learn More ]
There may be some component files that are hidden. Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden files and folders in the search result.  C:\Net-Temp.ini

Step 6

Restart in normal mode and scan your computer with your Trend Micro product for files detected as BKDR_FARFLI.DAA. If the detected files have already been cleaned, deleted, or quarantined by your Trend Micro product, no further step is required. You may opt to simply delete the quarantined files. Please check this Knowledge Base page for more information.


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