Classification

Category: Malware

Type: -

Aliases: Zasil, TrojanClicker.Win32.Zasil, Trojan.Zasil

Summary


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

MINENEW.EXE.PIF
MINENEW.MPG.PIF

Removal


Automatic action

Based on the settings of your F-Secure security product, it will either automatically delete, quarantine or rename the detected program or file, or ask you for a desired action.

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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 email.