ALIASES:

Backdoor:Win32/Zegost.B (Microsoft); Generic BackDoor!1fc (McAfee); Trojan.ADH (Symantec); Trojan.Win32.Jorik.Zegost.bjy (Kaspersky); Trojan.Win32.Generic!BT (Sunbelt); Trojan.Generic.6716887 (FSecure)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted:

  • 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.

It deletes itself after execution.

  TECHNICAL DETAILS

File Size: 340,099 bytes
File Type: EXE
Memory Resident: No
Initial Samples Received Date: 13 Jul 2012

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 creates the following folders:

  • %System Root%\Documents and Settings\Common
  • %System Root%\Documents and Settings\LocalServer
  • %Start Menu%\Programs\XXX

(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.. %Start Menu% is the current user's Start Menu folder, which is usually C:\Windows\Start Menu or C:\Documents and Settings\{User name}\Start Menu on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Roaming\Microsoft\Windows\Start Menu on Windows Vista and 7.)

Other System Modifications

This backdoor adds the following registry keys:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Control\MediaResources\msvideo

Dropping Routine

This backdoor drops the following files:

  • %User Profile%\Utility.dll
  • %User Profile%\boot.bat
  • %Start Menu%\Programs\XXX\calc.lnk
  • %Windows%\hello.bat
  • %System Root%\Documents and Settings\maomao.exe

(Note: %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista and 7.. %Start Menu% is the current user's Start Menu folder, which is usually C:\Windows\Start Menu or C:\Documents and Settings\{User name}\Start Menu on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Roaming\Microsoft\Windows\Start Menu on Windows Vista and 7.. %Windows% is the Windows folder, which is usually C:\Windows.. %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)

Other Details

This backdoor deletes itself after execution.

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine: 9.200

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

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\Control\MediaResources
    • msvideo

Step 3

Search and delete these components

[ Learn More ]
There may be some components 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 Profile%\Utility.dll
  • %User Profile%\boot.bat
  • %Start Menu%\Programs\XXX\calc.lnk
  • %Windows%\hello.bat
  • %System Root%\Documents and Settings\maomao.exe

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.
  • %System Root%\Documents and Settings\Common
  • %System Root%\Documents and Settings\LocalServer
  • %Start Menu%\Programs\XXX

Step 5

Scan your computer with your Trend Micro product to delete files detected as BKDR_ZEGOST_0000013.TOMA. 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.


Did this description help? Tell us how we did.