F-Secure Virus Descriptions : Anker.A

[Summary] | [Detailed Description] | [Detection]

NAME:	Anker.A
ALIAS:	Email-Worm.Win32.Anker.a, W32.Ahker.B@mm
SIZE:	13824

Summary

Anker is a simple e-mail worm that spreads itself inside a ZIP archive. The archive is downloaded from the Geocities webserver (from one of user accounts) just before spreading.

Detailed Description

The worm is written in Visual Basic. Its file is a UPX-packed PE executable 13824 bytes long. The unpacked worm's file size is over 61 kilobytes.

Installation to system

When the worm's file is run, it copies itself to Windows directory as SERVICES.EXE file and creates startup keys for this file in System Registry:

 [HKLM\Software\Microsoft\windows\CurrentVersion\Run
 "Norton Auto-Protect" = "SERVICES.EXE"

 [HKLM\software\microsoft\windows\currentversion\runservices-]
 "Windows Service" = "SERVICES.EXE"

 [HKLM\software\microsoft\windows\currentversion\windowsupdate]
 "auto update" = "SERVICES.EXE"

 [HKLM\software\microsoft\windows\currentversion\app paths
 "LUALL.exe" = "SERVICES.EXE"

 [HKCR\txtfile\shell\open\command]
 @ = "SERVICES.exe %1"

The worm also creates keys in the Registry that contain its name, version, source language, virus writer hadle and features list.

Additionally the worm copies itself to startup folders of all users.

The worm creates a text file named 'Norton AntiVirus.txt' in the root folder of C: drive and writes the following text there:

 Script Blocking: Disabled

Spreading in E-mails

The worm spreads itself in e-mail messages. It reads Outlook Address Book and sends an e-mail with its attached file to all found e-mail addresses. The worm sends the following message:

Subject:

 Service Pack 2 BUG!!

Body:

 Dear user I have been informed that there was a BUG in Windows
 Service Pack 2 which was fixed I recommend you to download this
 Patch version which will fix the bug and keep your system safe.

 You will find the Patch file in the attachment, feal free to
 send it to anyone.

 I'll be in touch with you as soon as another bug is found.

 Regards,
 A.H

Attachment:

 Fix_SP2.zip

The attachment is a ZIP archive with the worm's file named 'Fix_SP2.exe'. This ZIP archive is downloaded by the worm from an account on Geocities webserver before spreading. To get infected, a user has to extract and run the worm's file.

Payload

The worm modifies HOSTS file to block access to certain websites. The addresses of these websites are changed to localhost (127.0.0.1). Here's the list of the websites that the worm blocks access to:

 www.symantec.com
 www.microsoft.com
 www.wwe.com
 www.rohitab.com
 www.coderheaven.com
 www.astalavista.com
 www.google.com
 www.yahoo.com
 www.msn.com
 www.messenger.msn.com
 www.geocities.com
 www.worldsex.com
 www.cnn.com
 www.gamerevolution.com
 www.hackers.com
 www.fbi.gov
 www.hotmail.com
 www.norton.com
 www.idm.com

Additionally the worm modifies the Registry affecting security settings (firewall, autoupdate, anti-virus disable notifications, etc.). Also System Restore, 'Run' option in the Start Menu, Registry Tools and Task Manager get disabled. Certain applications are not allowed to run any more:

 Write
 Notepad
 Regedit
 Wordpad
 Wuauctl
 Wupdmgr
 MSN Messenger

The worm tries to change computer name, ProdictID of Windows and Internet Explorer to "Agent Hacker".

The worm also runs TASKKILL application to kill certain processes.

Back to the Top

Detection

Detection for this malware was published in the following F-Secure Anti-Virus updates:

[FSAV_Database_Version]

Version=2005-01-24_01

Back to the Top

Technical Details: Alexey Podrezov, February 2nd, 2005;

F-Secure Corporation