Virus	Activates	Effects	Released
Stoned	Immediately	Most common virus: Destroys or writes over important information on the hard disk and damages files.	1987
Michelangelo	March 6th	Infects every diskette inserted into a drive, formats the hard disk, corrupts or writes over important information on the hard disk, and damages files.
Disk Killer	After 48 hours of computer usage time	Encrypts all the document files on a hard disk, destroys or writes over important information on the hard drive, and damages files.
Dark Avenger

("Eddie")	After infecting every 16th file	Writes over a random part of the hard drive, damages files, and corrupts program files.	1989
Frodo	September 22nd	Corrupts program files, damages document files, and locks up system.	1989
Friday the 13th

(Jerusalem-B)	Friday 13th	Deletes any files used on Friday 13th, infects program files more than once so file sizes grow and, one-half hour after infection, slows down computer by 10 times.	1987
Hong Kong

(Azusa)	Immediately	Destroys files, corrupts document and program files, disables computer ports, and affects floppy drives so that DOS cannot recognize diskettes.
Ping-Pong

(Italian)	Randomly	Sends a white pong-like ball bouncing around the screen, and corrupts or writes over important information on the hard disk.
Yankee Doodle	5:00 p.m.	Plays Yankee Doodle, increases sizes of infected program files, and corrupts program files.
Joshi	January 5th	Asks you to type "Happy Birthday Joshi", then destroys or writes over important information on the hard disk, damages files, and corrupts document files.