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TROJ_DROPPER.OPL

October 08, 2012
 Analysis by: Christopher Daniel So
 PLATFORM:

Windows 2000, XP, Server 2003

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW


This Trojan deletes itself after execution.

  TECHNICAL DETAILS

File Size:

123,392 bytes

File Type:

EXE

File Compression:

Aspack

Memory Resident:

Yes

Initial Samples Received Date:

01 Sep 2010

Payload:

Drops files

Installation

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

  • %User Temp%\xvassdf.exe

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003.)

It drops the following file(s)/component(s):

  • %User Temp%\4tddfwq{random number}.dll - detected as TROJ_DROPPER.OPM

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003.)

It injects itself into the following processes running in the affected system's memory:

  • explorer.exe

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

  • explorer.exe

Autostart Technique

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

HKEY_CURRENT_USER\SoftWare\Microsoft\
Windows\CurrentVersion\Run
54dfsger = %User Temp%\xvassdf.exe

Other Details

This Trojan deletes itself after execution.

  SOLUTION

Minimum Scan Engine:

8.900

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

[ Learn More ]

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
    • 54dfsger=%User Temp%\xvassdf.exe

Step 4

Remove malware files dropped/downloaded by TROJ_DROPPER.OPL

    TROJ_DROPPER.OPM

Step 5

Scan your computer with your Trend Micro product to delete files detected as TROJ_DROPPER.OPL. 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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