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SemiSoft, Net.666


This virus infects Windows EXE files. It spreads natively under Windows 95 and NT (making it the fourth known Windows NT -specific virus).


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.

Technical Details

After infecting a machine and waiting for some time, the virus sends a "ping" to four IP addresses located in New Zealand to announce which machines it has infected. After this, the infected machines open up port 531 for incoming connections, and the machines can be controlled by sending commands to this port.

There are several variants. The first 60416 byte variant contains these texts:

mylen=, c:\testexe.exe, NOTEPADX.EXE, NOTEPAD.EXE, SETUP.EXE,
 ETHP v5.2

When the virus is active, it is visible in the process list as a number, typicly "6.666". When exiting Windows, NT sometimes complains it can't close a task by this name.

SemiSoft was known to be in the wild in the end of 1997 and beginning of 1998.