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BKDR_ZEGOST.CG

August 07, 2015
 ALIASES:

Backdoor:Win32/Zegost.AK (Microsoft); Downloader-AZV (McAfee); Backdoor.Trojan (Symantec); Trojan-Dropper.Win32.Agent.hvec (Kaspersky); Mal/Emogen-Y (Sophos); Could be a Trojan horse BackDoor.Delf (AVG)

 PLATFORM:

Windows

 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:

22,016 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

07 Aug 2015

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:

  • %Program Files%\Internet Explorer\WinHelp32.exe

(Note: %Program Files% is the Program Files folder, where it usually is C:\Program Files on all Windows operating system versions; C:\Program Files (x86) for 32-bit applications running on Windows 64-bit operating systems.)

Other System Modifications

This backdoor adds the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\WinHelp32
SYSTEM\CurrentControlSet\Services\WinHelp32 = "Windows Help System for X32 windows desktop"

Other Details

This backdoor connects to the following possibly malicious URL:

  • {BLOCKED}6.56.15

It deletes itself after execution.

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine:

9.750

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 value

[ 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\ControlSet001\Services\WinHelp32
    • SYSTEM\CurrentControlSet\Services\WinHelp32 = "Windows Help System for X32 windows desktop"

Step 3

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