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BKDR_SKSOCKET.AT

October 08, 2012
 Analysis by: JasperM
 PLATFORM:

Windows 2000, XP, 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 is the command line tool called SkServer.

This backdoor may be dropped by other malware.

It acts as a proxy server to allow remote malicious user to use the affected systems to hide their identities when performing malicious activities.

  TECHNICAL DETAILS

Ports:

User-specified

File Size:

40,960 bytes

File Type:

PE

Memory Resident:

Yes

Initial Samples Received Date:

21 Apr 2010

Arrival Details

This backdoor may be dropped by other malware.

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\SkServer
ImagePath = {malware path and file name}.EXE

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SkServer
Start = 2

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SkServer
DisplayName = Snake SockProxy Service

Proxy Server Routine

This backdoor acts as a proxy server to allow remote malicious user to use the affected systems to hide their identities when performing malicious activities.

Other Details

Based on analysis of the codes, it has the following capabilities:

  • Uses TCP port 1813 by default, but the remote malicious user can configure it to any port number.

  SOLUTION

Minimum Scan Engine:

8.900

FIRST VSAPI PATTERN FILE:

6.638.01

FIRST VSAPI PATTERN DATE:

19 Nov 2009

VSAPI OPR PATTERN File:

7.469.00

VSAPI OPR PATTERN Date:

17 Sep 2010

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

Identify and terminate files detected as BKDR_SKSOCKET.AT

[ Learn More ]
  1. If the detected file is displayed in either Windows Task Manager or Process Explorer but you cannot delete it, restart your computer in safe mode. To do this, refer to this link for the complete steps.
  2. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

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
    • SkServer

Step 4

Scan your computer with your Trend Micro product to delete files detected as BKDR_SKSOCKET.AT. 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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