Threat Description

Zasil

Details

Aliases:Zasil, TrojanClicker.Win32.Zasil, Trojan.Zasil
Category:Malware
Type:Trojan
Platform:W32

Summary



Zasil trojan appeared in the beginning of November 2002. It was sent to many users in e-mail with one of the following attachment names:

MINENEW.EXE.PIF
 MINENEW.MPG.PIF


Removal


Automatic action

Once detected, the F-Secure security product will automatically disinfect the suspect file by either deleting it or renaming it.

More

You may wish to refer to the Support Community for further assistance. You also may also refer to General Removal Instructions for a general guide on alternative disinfection actions.



Technical Details



When the trojan's file is run, it shows an x-rated picture, drops an executable file to temporary folder and runs it. This file copies itself as REGISTRY.EXE file into Windows folder and creates a startup key for itself in Windows Registry:

[HKLM\Software\Microsoft\Windows\CurrentVersion\Run]
 "Registry Services" = "%windir%\registry.exe"
 

On some operating system versions the trojan creates a different run key:

[HKCU\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer]
 Run = %windir%\registry.exe
 

The REGISTRY.EXE file is packed with UPX file compressor. When this file is run during every Windows session, it waits until a user connects to Internet and downloads a text file from an account at Geocities.com site. The downloaded file contains one or more URLs that the trojan tries to connect to. When the trojan connects to an URL, it adds information about user's IP address and the '<br>Second,email_zasil' string to the URL. This way the author of the trojan knows the IPs of computers where his trojan is installed.

Disinfection solution for this trojan is to delete its file and also to delete the dropper that came in e-mail.





Technical Details: Alexey Podrezov; F-Secure Corp., November 5th, 2002


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