BKDR_FARFLI.AHZ

 Analysis by: Mark Joseph Manahan

 ALIASES:

a variant of Win32/Farfli.FC trojan (Eset), Backdoor.Win32.Farfli (Ikarus), W32/Katusha.BN.worm (Panda), Trojan.Win32.Redosdru.C (v) (Sunbelt)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Spammed via email, Downloaded from the Internet, Dropped by other malware


This backdoor arrives as an attachment to email messages spammed by other malware/grayware or malicious users. It arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It runs certain commands that it receives remotely from a malicious user. Doing this puts the affected computer and information found on the computer at greater risk.

  TECHNICAL DETAILS

File Size:

245,928 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

05 Oct 2012

Payload:

Compromises system security, Connects to URLs/IPs

Arrival Details

This backdoor arrives as an attachment to email messages spammed by other malware/grayware or malicious users.

It 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 and executes them:

  • %Program Files%\Oklm\Tklmnopqr.jpg

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

It creates the following folders:

  • %Program Files%\Oklm

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

Autostart Technique

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

HKEY_LOCAL_MACHINE\SOFTWARE\{random number 1}\
Parameters
ServiceDll = "%Program Files%\Oklm\Tklmnopqr.jpg"

Other System Modifications

This backdoor adds the following registry keys:

HKEY_LOCAL_MACHINE\SOFTWARE\{random number 1}

HKEY_LOCAL_MACHINE\SOFTWARE\{random number 2}

HKEY_LOCAL_MACHINE\SOFTWARE\{random number 1}\
Parameters

HKEY_CURRENT_USER\NetSubKey

Backdoor Routine

This backdoor opens the following port(s) where it listens for remote commands:

  • 8000

It executes the following command(s) from a remote malicious user:

  • Screen Capture
  • Record audio and webcam video
  • List, Create and Delete Services
  • Start/Stop services
  • Log keyboard and mouse activities
  • Perform remote shell
  • Search/Manipulate Files
  • Get System Information

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

  • {BLOCKED}.{BLOCKED}.66.222

Other Details

This backdoor connects to the following URL(s) to get the affected system's IP address:

  • http://baidu.com/ip.txt

NOTES:

The C&C Server is obtained from the following URL:

  • user.{BLOCKED}e.qq.com/36907034

  SOLUTION

Minimum Scan Engine:

9.200

FIRST VSAPI PATTERN FILE:

9.440.07

FIRST VSAPI PATTERN DATE:

05 Oct 2012

VSAPI OPR PATTERN File:

9.441.00

VSAPI OPR PATTERN Date:

05 Oct 2012

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_FARFLI.AHZ

Step 3

Restart in Safe Mode

[ Learn More ]

Step 4

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.

  • In HKEY_LOCAL_MACHINE\SOFTWARE
    • {random number 1}
  • In HKEY_CURRENT_USER
    • NetSubKey

Step 5

Search and delete this folder

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result.  
  • %Program Files%\Oklm

Step 6

Restart in normal mode and scan your computer with your Trend Micro product for files detected as BKDR_FARFLI.AHZ. 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.

NOTES:

The created registry key HKEY_LOCAL_MACHINE\SOFTWARE\{random number 2} cannot be identified by the user since there are no reference values in the created key. The only way it can be identified is by comparing the present keys with a backup if the users have one. Note that the key need not to be deleted since it won't cause the user system any harm.


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