Modified by: Francis Xavier Antazo
ALIASES:

Backdoor:Win32/Zegost.B (Microsoft); Backdoor.Zegost (Malwarebytes);

 PLATFORM:

Windows

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: No

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

  TECHNICAL DETAILS

File Size: 152844 bytes
Memory Resident: Yes
Initial Samples Received Date: 05 Apr 2014

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.

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\System\CurrentControlSet\
Services\DirectX jrq

Backdoor Routine

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

  • Remote shell
  • Get arbitrary file content
  • Keyboard log
  • Get phonebook
  • Get user accounts
  • Establish remote desktop

NOTES:

This is the Trend Micro detection for damaged samples of BKDR_ZEGOST variants. These samples have coding errors that prevent them from properly executing their routines.

  SOLUTION

Minimum Scan Engine: 9.750
FIRST VSAPI PATTERN FILE: 11.924.05
FIRST VSAPI PATTERN DATE: 17 Sep 2015
VSAPI OPR PATTERN File: 11.925.00
VSAPI OPR PATTERN Date: 18 Sep 2015

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

Note that not all files, folders, and registry keys and entries are installed on your computer during this malware's/spyware's/grayware's execution. This may be due to incomplete installation or other operating system conditions. If you do not find the same files/folders/registry information, please proceed to the next step.

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. Before you could do this, you must restart in Safe Mode. For instructions on how to do this, you may refer to this page If the preceding step requires you to restart in safe mode, you may proceed to edit the system registry.

 
  • In HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services
    • DirectX jrq

Step 4

Scan your computer with your Trend Micro product to delete files detected as BKDR_ZEGOST.DAM. 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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