The computer virus has reached its 25th birthday. 'Elk Cloner' was created in July 1982, when it was added to a computer game and spread via floppy disks between Apple II systems. The creator is believed to have been a high-school student from Pittsburgh.

The game was set to play normally 49 times, but to release the virus on the 50th time of starting the game. However, the virus payload was to make a poem appear on infected users' screens.

While originally a prank, the virus paved the way for a torrent of annoying and more dangerous malware over the years.

"Today's malware is frequently malevolent and coded by criminals and/or hackers who are intent on extracting money from - as well as destroying the data of - innocent computer users and the organizations they work for," said Phil Higgins of security firm Brookcourt Solutions.

One of the first pieces of malware to trigger a global epidemic was Melissa, which was released in 1999 via an email attachment and is thought to have infected one million computers in North America alone.


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