Analysis by: Rika Joi Gregorio
ALIASES:

Backdoor:Win32/Zegost.AD(Microsoft), Win32/Farfli.AEE trojan(Eset)

 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: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel: Downloaded from the Internet, Dropped by other malware

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 executes commands from a remote malicious user, effectively compromising the affected system. It connects to a website to send and receive information.

  TECHNICAL DETAILS

File Size: 89,445 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 07 Sep 2013
Payload: 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 copies of itself into the affected system and executes them:

  • %Windows%\{random}.exe

(Note: %Windows% is the Windows folder, which is usually C:\Windows.)

It drops the following files:

  • %System%\MODIf.html

(Note: %System% is the Windows system folder, which is usually C:\Windows\System32.)

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\Ghijkl Nopqrstu Wxy
Image Path = "%Windows%\qagmse.exe"

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

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Ghijkl Nopqrstu Wxy

Backdoor Routine

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

  • Logs Keystroke
  • Get clipboard data
  • Clear clipboard data
  • Logs Mouse event
  • Capture screenshot
  • Download and Execute files
  • List/start services
  • Create hidden administrative user
  • Perform remote shell

It connects to the following websites to send and receive information:

  • {BLOCKED}.39.40:8001
  • aspkeyee.{BLOCKED}p.net

  SOLUTION

Minimum Scan Engine: 9.300
FIRST VSAPI PATTERN FILE: 10.264.04
FIRST VSAPI PATTERN DATE: 07 Sep 2013
VSAPI OPR PATTERN File: 10.265.00
VSAPI OPR PATTERN Date: 08 Sep 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\SYSTEM\CurrentControlSet\Services
    • Ghijkl Nopqrstu Wxy

Step 4

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%\MODIf.html

Step 5

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