BKDR_ZEGOST.SMT

December 16, 2013
 Analysis by: Nikko Tamana
 ALIASES:

Backdoor:Win32/Farfli.K (Microsoft), Win32/Farfli.DP trojan (NOD32), Backdoor.Ghostnet (Norton)

 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:
 INFORMATION EXPOSURE:

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Dropped by other malware, Downloaded from the Internet

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 does not have any propagation routine.

It executes commands from a remote malicious user, effectively compromising the affected system.

  TECHNICAL DETAILS

File Size:

103,936 bytes

File Type:

DLL

Memory Resident:

Yes

Initial Samples Received Date:

10 Dec 2013

Payload:

Compromises system security, Connects to URLs/IPs

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 file(s)/component(s):

  • %System Root%\Net-Temp.ini – Non-malicious

(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)

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

  • %Program Files%\Mwoo\Gqwdpfieg.gif

(Note: %Program Files% is the default Program Files folder, usually C:\Program Files in Windows 2000, Server 2003, and XP (32-bit), Vista (32-bit), and 7 (32-bit), or C:\Program Files (x86) in Windows XP (64-bit), Vista (64-bit), and 7 (64-bit).)

It creates the following folders:

  • %Program Files%\Mwoo

(Note: %Program Files% is the default Program Files folder, usually C:\Program Files in Windows 2000, Server 2003, and XP (32-bit), Vista (32-bit), and 7 (32-bit), or C:\Program Files (x86) in Windows XP (64-bit), Vista (64-bit), and 7 (64-bit).)

It injects itself into the following processes as part of its memory residency routine:

  • Svchost.exe

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\Software\{random numbers}\
Parameters
ServiceDll = “%Program Files%\Mwoo\Gqwdpfieg.gif”

HKEY_LOCAL_MACHINE\System\CurrentControlSet\
Services\{service}
ImagePath = "%System%\svchost.exe -k imgsvc"

HKEY_LOCAL_MACHINE\Software\{random numbers}
imgsvc = "{service}"

Other System Modifications

This backdoor adds the following registry keys:

HKEY_LOCAL_MACHINE\Software\{random numbers}

HKEY_LOCAL_MACHINE\System\CurrentControlSet\
Services\{service}

Propagation

This backdoor does not have any propagation routine.

Backdoor Routine

This backdoor executes the following commands from a remote malicious user:

  • File manager
  • Screen control
  • List running processes
  • Keylogger
  • Remote shell execution
  • Activate web cam
  • Voice monitoring via installed microphone
  • List dial-up profiles
  • Block keyboard and mouse
  • Block screen
  • Shutdown/restart machine
  • Download and execute file/s

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

  • 1.{BLOCKED}7.com

NOTES:

It does not have rootkit capabilities.

It does not exploit any vulnerability.

  SOLUTION

Minimum Scan Engine:

9.700

VSAPI OPR PATTERN File:

10.469.00

VSAPI OPR PATTERN Date:

13 Dec 2013

Step 1

Before doing any scans, Windows XP, Windows Vista, and Windows 7 users must disable System Restore to allow full scanning of their computers.

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.

 
  • In HKEY_LOCAL_MACHINE\Software
    • {random numbers}
  • In HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services
    • {service}

Step 4

Search and delete these folders

[ 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%\Mwoo

Step 5

Search and delete this file

[ Learn More ]
There may be some 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.
  • %System Root%\Net-Temp.ini

Step 6

Restart in normal mode and scan your computer with your Trend Micro product for files detected as BKDR_ZEGOST.SMT. 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:

To delete the registry key HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\{service}:

Please note the registry value in HKEY_LOCAL_MACHINE\Software\{random numbers} imgsvc = "{service}"


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