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BKDR_ZEGOST.SMED

April 11, 2013
 Analysis by: Nikko Tamana
 ALIASES:

W32/Agent.OWW!tr (Fortinet), W32/PcClient.A.gen!Eldorado (FProt), Trojan.Win32.Yoddos (Ikarus), Trojan.Win32.Scar.ftjg (Kaspersky), Backdoor:Win32/Zegost.AK (Microsoft), Win32/Agent.OWW trojan (NOD32), Trojan.Peed.Gen (Bitdefender)

 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:

  • 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 deletes itself after execution.

  TECHNICAL DETAILS

File Size:

Varies

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

03 Dec 2012

Payload:

Compromises system security, Collects system information, 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:

  • %System%\Wi808b.exe

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

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

  • zrp.minipokesa.com:8008

It injects itself into the following processes as part of its memory residency routine:

  • svchost.exe

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\W808bjf32
ImagePath = "%System%\Wi808b.exe"

Other System Modifications

This backdoor adds the following registry keys:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\W808bjf32

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\W808bjf32\Security

It adds the following registry entries as part of its installation routine:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\W808bjf32
Type = "10"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\W808bjf32
Start = "2"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\W808bjf32
ErrorControl = "0"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\W808bjf32
DisplayName = "Wi808bs Heay System"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\W808bjf32
ObjectName = "LocalSystem"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\W808bjf32
SYSTEM\CurrentControlSet\Services\W808bjf32 = "Wi808bs Hhlm System for X32"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\W808bjf32\Security
Security = "{Random Hex Values}"

Backdoor Routine

This backdoor opens the following port(s) where it listens for remote commands:

  • TCP Port 8008

It executes the following commands from a remote malicious user:

  • Perform DDOS attacks
  • Release mutex
  • Terminate itself
  • Delete itself
  • Delete its added service registry
  • Remote shell execution
  • Download and execute files
  • Shutdown machine

It connects to the following URL(s) to send and receive commands from a remote malicious user:

  • {BLOCKED}p.{BLOCKED}kesa.com

It posts the following information to its command and control (C&C) server:

  • Processor information
  • OS version information
  • Current usage of both physical and virtual memory
  • Install language information

Other Details

This backdoor deletes itself after execution.

  SOLUTION

Minimum Scan Engine:

9.300

FIRST VSAPI PATTERN FILE:

9.568.05

FIRST VSAPI PATTERN DATE:

03 Dec 2012

VSAPI OPR PATTERN File:

9.569.00

VSAPI OPR PATTERN Date:

04 Dec 2012

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
    • W808bjf32

Step 4

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