Analysis by: Michael Cabel
 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

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 opens a random port to allow a remote user to connect to the affected system. Once a successful connection is established, the remote user executes commands on the affected system.

  TECHNICAL DETAILS

File Size: 37,376 bytes
File Type: PE
Memory Resident: Yes
Initial Samples Received Date: 26 Jun 2009
Payload: Steals information

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 component file(s):

  • %System%\dssemh.dll - also detected as BKDR_HUPIGON.ZXS

(Note: %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.)

Its DLL component is injected to the following process(es):

  • SVCHOST.EXE

Autostart Technique

This backdoor adds the following registry entries to enable its automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\6to4\Parameters
ServiceDll = %System%\dssemh.dll

Backdoor Routine

This backdoor opens a random port to allow a remote user to connect to the affected system. Once a successful connection is established, the remote user executes commands on the affected system.

NOTES:

This backdoor gathers the following system information from the affected system:

  • Computer Name
  • IP Address
  • OS Version and Build
  • System's Language

It may perform the following actions to the affected system:

  • Delete files and folders
  • Download and execute files
  • List files and folders
  • List installed drives
  • Terminate process

  SOLUTION

Minimum Scan Engine: 9.200
FIRST VSAPI PATTERN FILE: 6.226.03
FIRST VSAPI PATTERN DATE: 26 Jun 2009

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

Restart in Safe Mode, and then 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
    • 6to4

Step 3

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