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Aliases :

Shell, Tentacle_II


This virus was found in the wild in June 1996 in USA, UK, Australia, Norway and New Zealand. It has possibly been distributed over the internet several times.


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

A known infection happened on the 3rd of August, 1996, when an infected screen saver called PCTRSHOW.ZIP was posted to the following newsgroups:

Do note that there are also clean copies of PCTRSHOW in circulation.

The virus infect only Windows 3.x executables (NE), and it does it without changing the executable entry point. This is an unusual infection method and was first introduced in this virus.

When executed, Shell.10634 searches the directory tree for suitable files to infect. Only EXE and SCR (screen saver) files can get infected.

Also 32bit Win95 and WinNT executables can be infected by the virus, but these files are unable to spread the infection further. Shell not stay resident in memory.

This virus activates by dropping a GIF file, which contains a picture of a Tentacle and text:

I'm the Tentacle Virus!

The author of this virus also wrote the Tentacle and Tentatrickle viruses, which are technically quite different from this virus. See: Tentacle