WORM_STEKCT.A

October 09, 2012
 Analysis by: Kathleen Notario
 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

This worm arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It connects to certain websites to send and receive information.

  TECHNICAL DETAILS

File Size:

172,179 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

16 Feb 2012

Arrival Details

This worm 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 worm drops the following copies of itself into the affected system:

  • %Windows%\mdm.exe

(Note: %Windows% is the Windows folder, which is usually C:\Windows or C:\WINNT.)

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

  • Microsoft Browser Engine

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Microsoft Firevall Engine = "%Windows%\mdm.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
Microsoft Firevall Engine = "%Windows%\mdm.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Terminal Server\
Install\Software\Microsoft\
Windows\CurrentVersion\Run
Microsoft Firevall Engine = "%Windows%\mdm.exe"

Other System Modifications

This worm adds the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\AuthorizedApplications\
List
%Windows%\mdm.exe = "%Windows%\mdm.exe:*:Enabled:MSN Messenger"

Process Termination

This worm terminates the following processes if found running in the affected system's memory:

  • YahooAUService.exe
  • ekrn.exe
  • egui.exe
  • msseces.exe

Other Details

This worm connects to the following website to send and receive information:

  • ms.{BLOCKED}kva.su

NOTES:

It may also drop copies of itself in the following directories:

  • %Program Files%
  • %Public%

It disables the following services if found running in the affected system:

  • YahooAUService
  • ekrn
  • MsMpSvc
  • wuauserv

It sends messages that contain links to sites hosting malicious files/copies of itself using the following instant-messaging (IM) applications/social networks:

  • AIM
  • Facebook
  • Google Talk
  • ICQ
  • Skype
  • Windows Live Messenger
  • Yahoo! Messenger

  SOLUTION

Minimum Scan Engine:

9.200

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 WORM_STEKCT.A

[ 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 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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • Microsoft Firevall Engine = "%Windows%\mdm.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • Microsoft Firevall Engine = "%Windows%\mdm.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Terminal Server\Install\Software\Microsoft\Windows\CurrentVersion\Run
    • Microsoft Firevall Engine = "%Windows%\mdm.exe"
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\AuthorizedApplications\List
    • %Windows%\mdm.exe = "%Windows%\mdm.exe:*:Enabled:MSN Messenger"

Step 4

Scan your computer with your Trend Micro product to delete files detected as WORM_STEKCT.A. 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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