25 years have passed since the first computer virus Elk Cloner first infected a computer. Almost a harmless creature of a computer code did not cause much damage beyond making a poem appear on infected users' screens. It is believed that Elk Cloner was written by a fifteen-year-old high school student named Rich Skrenta for Apple II systems.

Computer viruses in their classic form are almost dead today. Today, considerably more danger comes from malware. Intentionally or without any intentions, computer viruses cause a lot of trouble. The first virus to cause damage on a colossal scale was Melissa - a computer worm released in 1999 via an e-mail. Melissa infected over one million computers in North America alone.

Even more danger comes from malware created by criminals. A simple Internet Explorer plugin that may look as an absolutely normal software can hijack your internet banking details. Users of Internet payment systems (PayPal, Moneybookers, NETeller and others) have been victims of such dangerous plugins many times.

Some people believe that the first virus ever created was called "Pervading Animal". It appeared in 1975 on the Univax 1108 system. If this theory is true, than a computer virus is considerably older. Frankly, I don't know if the tale about "Pervading Animal" is true but even if it is still Happy Birthday to Elk Cloner.