Analysis by: Cris Nowell Pantanilla
 PLATFORM:

Windows 98, ME, NT, 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 arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites. However, as of this writing, the said sites are inaccessible.

It connects to Internet Relay Chat (IRC) servers. It executes commands from a remote malicious user, effectively compromising the affected system.

It accesses websites to download files. This action allows this malware to possibly add other malware on the affected computer.

  TECHNICAL DETAILS

File Size: Varies
File Type: EXE
Memory Resident: Yes

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.

However, as of this writing, the said sites are inaccessible.

Installation

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

  • %System%\mdm.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.)

Backdoor Routine

This Trojan connects to any of the following Internet Relay Chat (IRC) servers:

  • mix.gruenb.com

It executes the following commands from a remote malicious user:

  • Posting Scanning
  • Create/Terminate Processes
  • Create/Terminate/Scan Thread
  • Join IRC
  • Send Private Messages
  • Delete Files
  • Download Files

Download Routine

This Trojan accesses websites to download the following files:

  • http://rsfq.info/demo.exe

  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

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 Visual Debuger = %System%\mdm.exe
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • Microsoft Visual Debuger = %System%\mdm.exe

Step 3

Restore this modified 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_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa
    • From: restrictanonymous = 1
      To: restrictanonymous = 0
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Ole
    • From: EnableDCOM = N
      To: EnableDCOM = Y

Step 4

Scan your computer with your Trend Micro product to delete files detected as TROJ_BUZUS.APR. 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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