Summary

Hamster is a simple virus found from Norway at the end of April 1993. It managed to become quite widespread through bbs systems. Hamster infects COM-files in the current directory by appending it's own code to the end of the host files and patching the first three bytes to transfer the control to the viruscode.

Additional Details

Effective length of the virus is 546 bytes. It will infect all COM files unless they are already infected or if they are EXE files renamed to COM (the virus checks this by the magic number "MZ" in the beginning of EXE files).

Virus will not stay resident in memory, and it seems to infect one file at a time. It will not alter host files time or date fields.

The virus carries the names of the new and old host files within it's code. It also has one text string: "Turbo Hamster Virus!".

[Analysis: Mikko Hypponen, F-Secure]