Analysis by: Roland Marco Dela Paz
ALIASES:

Microsoft : Trojan:Win32/Ragterneb.A; Kaspersky : Trojan.Win32.Vilsel.awhi

 PLATFORM:

Windows 2000, XP, 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 opens a hidden Internet Explorer window. It connects to a website to send and receive information.

It modifies the Internet Explorer Zone Settings.

  TECHNICAL DETAILS

File Size: 139,264 bytes
File Type: PE
Memory Resident: Yes
Initial Samples Received Date: 03 Dec 2010

Installation

This Trojan drops the following non-malicious file:

  • %Current%\userid.dat

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
{malware file name} = {malware path and file name}

Other System Modifications

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Internet Settings\
5.0\User Agent
@ = {user agent information}

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Internet Settings\
5.0\User Agent
@ = {user agent information}

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
System
DisableTaskMgr = 1

Backdoor Routine

This Trojan opens a hidden Internet Explorer window.

It connects to the following websites to send and receive information:

  • http://www.{BLOCKED}n.com/65/nua.php
  • http://{BLOCKED}teronline.in/

Web Browser Home Page and Search Page Modification

This Trojan modifies the Internet Explorer Zone Settings.

  SOLUTION

Minimum Scan Engine: 8.900
VSAPI PATTERN File: 7.674.03
VSAPI PATTERN Date: 03 Dec 2010
VSAPI PATTERN Date: 12/3/2010 12:00:00 AM

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\Internet Settings\5.0\User Agent
    • @ = {user agent information}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\5.0\User Agent
    • @ = {user agent information}
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\System
    • DisableTaskMgr 1
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • {malware file name} = {malware path and file name}

Step 4

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. %Current%\userid.dat

Step 5

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