Zasil trojan appeared in the beginning of November 2002. It was sent to many users in email with one of the following attachment names:
Based on the settings of your F-Secure security product, it will either move the file to the quarantine where it cannot spread or cause harm, or remove it.
A False Positive is when a file is incorrectly detected as harmful, usually because its code or behavior resembles known harmful programs. A False Positive will usually be fixed in a subsequent database update without any action needed on your part. If you wish, you may also:
Check for the latest database updates
First check if your F-Secure security program is using the latest updates, then try scanning the file again.
Submit a sample
After checking, if you still believe the file is incorrectly detected, you can submit a sample of it for re-analysis.
Note: If the file was moved to quarantine, you need to collect the file from quarantine before you can submit it.
Exclude a file from further scanning
If you are certain that the file is safe and want to continue using it, you can exclude it from further scanning by the F-Secure security product.
Note: You need administrative rights to change the settings.
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.
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