F-Secure Virus Descriptions : KLF

The virus installs itself in memory by copying itself into the interrupt vector table at 0000:0200. Virus infects all executed COM files which are between 6 bytes and 60 kilobytes. Virus doesn't reinfect infected files; it determines whether the file in question is infected by searching for KLF starting at offset 3 in the file. Virus preserves file attributes and date/time.

This virus does nothing except for messing up the interrupt table and spreading itself around.