Analysis by: Sabrina Lei Sioting
 PLATFORM:

Windows 98, ME, NT, 2000, XP, 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 modifies Internet Explorer security settings. This puts the affected computer at greater risk, as it allows malicious URLs to be accessed by the computer.

  TECHNICAL DETAILS

File Size: 2,066,944 bytes
File Type: PE
Memory Resident: No
Initial Samples Received Date: 06 Aug 2010
Payload: Connects to URLs/Ips, Displays message/message boxes

Installation

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

  • %Program Files%\AnVi\avt.exe

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

It drops the following file(s)/component(s):

  • %User Temp%\4otjesjty.mof

(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.)

It creates the following folders:

  • %Program Files%\AnVi

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

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
Antivirus = "%Program Files%\AnVi\avt.exe" -noscan

Other System Modifications

This Trojan adds the following registry keys:

HKEY_LOCAL_MACHINE\SOFTWARE\AnVi
=

(Note: The default value data of the said registry entry is .)

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

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\Main
Use FormSuggest = Yes

Web Browser Home Page and Search Page Modification

This Trojan modifies Internet Explorer zone settings.

Download Routine

This Trojan saves the files it downloads using the following names:

  • %User Temp%\avt.dat
  • %User Temp%\avtr.dat

(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 Details

Based on analysis of the codes, it has the following capabilities:

  • It displays fake alerts that warn users of infection. It also displays fake scanning results of the affected system. It then asks for users to purchase it once scanning is completed. If users decide to purchase the rogue product, users are directed to a certain Web site asking for sensitive information, such as credit card numbers.

It attempts to access the following websites to download files, which are possibly malicious:

  • http://{BLOCKED}eager.com/avt/avt_db
  • http://{BLOCKED}eager.com/avt/avt.dat
  • http://{BLOCKED}eager.com/avt/avtr.dat
  • http://{BLOCKED}eager.com/customers/getbuild.php
  • http://{BLOCKED}eager.com/avt/avt_db

  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\Internet Explorer\Main
    • Use FormSuggest = Yes
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • Antivirus = %Program Files%\AnVi\avt.exe -noscan

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.

  • In HKEY_LOCAL_MACHINE\SOFTWARE\
    • AnVi

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. %User Temp%\4otjesjty.mof
%User Temp%\avt.dat
%User Temp%\avtr.dat

Step 5

Scan your computer with your Trend Micro product to delete files detected as TROJ_FAKEAV.KTD. 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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