Analysis by: Sabrina Lei Sioting
 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

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

It executes the dropped file(s). As a result, malicious routines of the dropped files are exhibited on the affected system.

  TECHNICAL DETAILS

File Size: 401,511 bytes
File Type: EXE
Memory Resident: No
Initial Samples Received Date: 19 Jun 2012

Arrival Details

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

It may be dropped by the following malware:

  • TROJ_HWPEXPL.VTG

Installation

This Trojan creates the following folders:

  • %User Temp%\49e91302

(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.)

Other System Modifications

This Trojan adds the following registry entries as part of its installation routine:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Enum\Root\LEGACY_8D01DF96\
0000
Service = "8d01df96"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Enum\Root\LEGACY_8D01DF96\
0000
Class = "LegacyDriver"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Enum\Root\LEGACY_8D01DF96\
0000
ClassGUID = "{8ECC055D-047F-11D1-A537-0000F8753ED1}"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\8d01df96
ImagePath = "%System%\rundll32.exe "%Program Files%\Common Files\Microsoft Shared\Triedit\8d01df96.dll",ServiceEntry"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\8d01df96
DisplayName = "8d01df96"

It adds the following registry keys as part of its installation routine:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Enum\Root\LEGACY_8D01DF96

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\8d01df96

Dropping Routine

This Trojan drops the following files:

  • %Program Files%\Common Files\Microsoft Shared\Triedit\8d01df96.dll

(Note: %Program Files% is the default Program Files folder, usually C:\Program Files.)

It executes the dropped file(s). As a result, malicious routines of the dropped files are exhibited on the affected system.

  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

Remove the malware/grayware file that dropped/downloaded TROJ_DROPPER.SLS

     TROJ_HWPEXPL.VTG

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. Before you could do this, you must restart in Safe Mode. For instructions on how to do this, you may refer to this page If the preceding step requires you to restart in safe mode, you may proceed to edit the system registry.

  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\Root
    • LEGACY_8D01DF96
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services
    • 8d01df96

Step 4

Search and delete these folders

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result. %User Temp%\49e91302

Step 5

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. %Program Files%\Common Files\Microsoft Shared\Triedit\8d01df96.dll

Step 6

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