Back in 1982 the first computer virus was unleashed on an unsuspecting public by a ninth-grader who sought to play a practical joke to his friends. Rich Skrenta, now 40, created the self-replicating "Elk Cloner" which spread through Apple II floppy disks and displayed a poem written by him.

Twenty five years later, viruses have evolved to gain more destructive properties such as wiping documents or stealing sensitive data. The Times of India has compiled an interesting list of the most notorious viruses in PC history including some of the most recent ones such as the Blaster and Sasser worms.

Viruses have found several platforms: instant-messaging, file-sharing software, rogue web sites; images etc. As these malicious programmes go more sophisticated and their numbers increase on a daily basis, here's a look into some of the most notorious virus attacks over the last twenty-five years.