This is a simple virus with an uncommon activation routine: on some machines, it turns the the BIOS boot-up password on and changes the password to 'monica'.
Do not confuse this virus with Monika.686, which is a totally different virus.
Disinfection & Removal
Allow F-Secure Anti-Virus to disinfect the relevant files.
For more general information on disinfection, please see Removal Instructions.
Description Created: Mikko Hypponen, F-Secure