Gallery: Ten computer viruses that changed the world

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It's almost 25 years since the first PC computer virus left users looking at corrupted floppies, lost work and perplexing messages. In that time, the state of the art in automated malfeasance has progressed to the point that it's part of the armory of international geopolitics. Stuxnet, while still mysterious, left nobody in any doubt that viruses and worms can be used in the highest-stake game there is.

Along the way, hundreds of millions of infections have taken place, billions of dollars have been lost in productivity and broken systems, and the anti-malware industry has grown to become a significant player in the IT market. It's not over yet: perhaps it never will be, but the history of malware is a fascinating insight into the technology and culture of the digital world.

1. Brain (1986)
It sounded like science fiction, but it was all too real. Basit and Amjad Farooq Alvi, a pair of software programmers from Pakistan, became annoyed at people duplicating their products and created what was supposed to be a kill switch for illicit copies. But the design was flawed; the anti-copy software could duplicate itself — and did.

The first worldwide PC virus, Brain worked by changing the boot sector of a floppy. When an infected floppy was put into a computer, it installed Brain in the computer's memory, from where it infected new floppies as they were inserted.

The brothers included their names, address and phone numbers in the virus, ostensibly to offer their services to decontaminate infected computers. They subsequently regretted this.

Photo credit: Avinash Meetoo/Wikipedia

Captions: Rupert Goodwin, ZDNet UK