Threat Description



Category: Malware
Platform: W32
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.


Automatic action

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

More scanning & removal options

More information on scanning or removal options is available in the documentation for your F-Secure security product on the Downloads section of our Home - Global site.

You may also refer to the Knowledge Base on the F-Secure Community site for more information.

Contact Support

For further assistance, F-Secure customers can request support online via the Request support or the Chat forms on our Home - Global site.

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

Description Details: Mikko Hypponen, F-Secure


Suspect a file or URL was wrongly detected? Submit a sample to our Labs for analysis

Submit Now

Give And Get Advice

Give advice. Get advice. Share the knowledge on our free discussion forum.

Learn More