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: 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 scans the computer for registry keys related to antivirus and security applications. This action allows the malware to possibly avoid detection in the computer.

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

  TECHNICAL DETAILS

File Size: 225,280 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 08 Jun 2011
Payload: Terminates processes, Connects to URLs/IPs, Downloads files

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 drops the following component file(s):

  • %System%\PDFRAME.sys - detected as RTKT_AGENT.CLM

(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.)

Other System Modifications

This Trojan adds the following registry keys:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\PDFRAME
ImagePath = "%System%\PDFRAME.sys"

It scans the system for the following registry keys, which are related to antivirus and security applications:

HKEY_LOCAL_MACHINE\SOFTWARE\McAfee

HKEY_LOCAL_MACHINE\SOFTWARE\Doctor Web

Backdoor Routine

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

  • {BLOCKED}wn.tzh.kr

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

NOTES:
It is capable of the following commands:

  • Protect malware files
  • Create/terminate processes
  • Create/terminate services
  • List dial-up account and passwords
  • View system details
  • API hooking
  • Create/delete/modify user accounts
  • Download/upload files
  • Keylogging

  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

Remove malware files dropped/downloaded by BKDR_RIRLGED.A

    RTKT_AGENT.CLM

Step 3

Identify and delete files detected as BKDR_RIRLGED.A using either the Startup Disk or Recovery Console

[ Learn More ]

Step 4

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.

 
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services
    • PDFRAME

Step 5

Scan your computer with your Trend Micro product to delete files detected as BKDR_RIRLGED.A. 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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