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BKDR_MOSUCK.AMF

October 09, 2012
 Analysis by: Sabrina Lei Sioting
 ALIASES:

Backdoor:Win32/Mosucker.AA (Microsoft), Backdoor.Win32.MoSucker.30.az, Backdoor.Win32.MoSucker.30.az (Kaspersky), Backdoor.Mosuck (Symantec), BackDoor-EE!a (McAfee), W32/MoSucker.C.gen!Eldorado (Authentium), W32/MoSucker_30.AZ!tr.bdr (Fortinet), W32/MoSucker.C.gen!Eldorado (Fprot), Backdoor.Win32.VB (Ikarus), Win32/VB.NZH trojan (Eset), Backdoor W32/Mosuck.AGQ (Norman), Bck/Mosucker.CH (Panda),

 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

Infection Channel:

Downloaded from the Internet


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.

  TECHNICAL DETAILS

File Size:

163,840 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

01 Sep 2010

Payload:

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%\Updater.exe

(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.)

It drops the following component file(s):

  • %System%\mswinsck.ocx

(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.)

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Windows Update = "%System%\Updater.exe"

Backdoor Routine

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

  • 667

It executes the following commands from a remote malicious user:

  • Download and execute other files
  • Upload files
  • Log keystrokes or steal sensitive data
  • Run or terminate applications
  • Delete files

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

  • {BLOCKED}.blogdns.com
  • {BLOCKED}.103

As of this writing, the said servers are currently inaccessible.

  SOLUTION

Minimum Scan Engine:

9.200

FIRST VSAPI PATTERN FILE:

7.428.01

FIRST VSAPI PATTERN DATE:

01 Sep 2010

VSAPI OPR PATTERN File:

7.429.00

VSAPI OPR PATTERN Date:

02 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

Terminate the malware/grayware/spyware process:

[ Learn More ]
  • For Windows 98 and ME users, Windows Task Manager may not display all running processes. In this case, please use a third-party process viewer, preferably Process Explorer, to terminate the malware/grayware/spyware file. You may download the said tool here.
  • 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.
  • 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
      • Windows Update = "%System%\Updater.exe"

    Step 4

    Search and delete these files

    [ Learn More ]
    There may be some component files that are hidden. Please make sure you check the Search Hidden Files and Folders checkbox in the "More advanced options" option to include all hidden files and folders in the search result.
    • %System%\mswinsck.ocx

    Step 5

    Scan your computer with your Trend Micro product to delete files detected as BKDR_MOSUCK.AMF. 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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