Threat Encyclopedia

BKDR_ZEGOST.AZ

Publish date: October 09, 2012

ANALYSIS BY

Rhena Inocencio


ALIASES:

Backdoor:Win32/Zegost.AD (Microsoft), Trojan.Win32.Agent.sybw (Kaspersky), a variant of Win32/Farfli.OA trojan (ESET), Trojan.Win32.Generic!BT (Sunbelt)

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

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 may be dropped by other malware.

It does not have any propagation routine.

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

It does not have any downloading capability.

It does not have any information-stealing capability.

It deletes the initially executed copy of itself.

TECHNICAL DETAILS

File Size:

106,699 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

05 Aug 2012

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.

It may be dropped by the following malware:

  • TROJ_ARTIEF.CK

Installation

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

  • %User Temp%\1111111.exe

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003.)

It drops the following component file(s):

  • %User Temp%\00
  • %User Temp%\1111111.dll - detected as BKDR_ZEGOST.AZ
  • %User Temp%\config.txt - contains the encrypted remote address

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003.)

It adds the following mutexes to ensure that only one of its copies runs at any one time:

  • 1111111 Is Running!

Autostart Technique

This backdoor drops the following shortcut pointing to its copy in the User Startup folder to enable its automatic execution at every system startup:

  • %User Startup%\xxxxxxxx.lnk

(Note: %User Startup% is the current user's Startup folder, which is usually C:\Windows\Profiles\{user name}\Start Menu\Programs\Startup on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Start Menu\Programs\Startup on Windows NT, and C:\Documents and Settings\{User name}\Start Menu\Programs\Startup.)

Propagation

This backdoor does not have any propagation routine.

Backdoor Routine

This backdoor opens a hidden Internet Explorer window.

It executes the following commands from a remote malicious user:

  • Perform remote shell commands

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

  • http://{BLOCKED}0.{BLOCKED}0.35.60:2002
  • https://{BLOCKED}0.{BLOCKED}0.35.60:2002

Download Routine

This backdoor does not have any downloading capability.

Information Theft

This backdoor does not have any information-stealing capability.

Other Details

This backdoor deletes the initially executed copy of itself

NOTES:

It does not have rootkit capabilities.

It does not exploit any vulnerability.

SOLUTION

Minimum Scan Engine:

9.200

FIRST VSAPI PATTERN FILE:

9.308.03

FIRST VSAPI PATTERN DATE:

05 Aug 2012

VSAPI OPR PATTERN File:

9.309.00

VSAPI OPR PATTERN Date:

06 Aug 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

Remove the malware/grayware file that dropped/downloaded BKDR_ZEGOST.AZ

Step 3

Restart in Safe Mode

[ Learn More ]

Step 4

Search and delete these files

[ 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.
  • %User Temp%\00
  • %User Temp%\1111111.dll
  • %User Temp%\1111111.exe
  • %User Temp%\config.txt

Step 5

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