Analysis by: Cris Nowell Pantanilla
 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: No

  • 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.

As of this writing, the said sites are inaccessible.

  TECHNICAL DETAILS

File Size: 19,968 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 19 Dec 2008

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.

Installation

This Trojan injects threads into the following normal process(es):

  • svchost.exe

Download Routine

This Trojan accesses the following websites to download files:

  • http://{BLOCKED}dio.com/query.asp

As of this writing, the said sites are inaccessible.

NOTES:
It renames the normal file %System%\dmserver.dll to %System%\tdmserver.dll. It then drops the malicious file %System%\dmserver.dll(also detected as TROJ_AGENTT.AI). This causes the malware to execute if other files attempts to use the normal dmserver.dll.

  SOLUTION

Minimum Scan Engine: 9.200
FIRST VSAPI PATTERN FILE: 5.720.05
FIRST VSAPI PATTERN DATE: 19 Dec 2008

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

Scan your computer with your Trend Micro product and note files detected as TROJ_AGENTT.AI

Step 3

Restart in Safe Mode

[ Learn More ]

Step 4

Search and delete the file detected as TROJ_AGENTT.AI

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden files in the search result.

Step 5

Restoring a File to its Original Location

  1. Click Start>Run.
  2. In the text box, type the following:
    command /c copy  %System%\tdmserver.dll %System%\dmserver.dll
  3. Press Enter.

Step 6

Restart in normal mode and scan your computer with your Trend Micro product for files detected as TROJ_AGENTT.AI. 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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