Defence experts working to beat threat.
Defence experts are working to stop anarchists and terrorists from spreading chaos by planting tiny programs in computer systems.
Soon after September 11, President Bush appointed America's first cybersecurity czar, Richard Clarke. Cardiff University's Professor RR Martin said he was sure deliberate attacks on computer systems would become more common in the future. He expects the British defence establishment are also developing similarly destructive programs.
Prof Martin's computer was infected with a virus in 1992 which was traced back to three students at Cornell University, the prestigious American Ivy League college.
He said, ``I think it's not that they were doing it malevolently; it was more the intellectual challenge.''
The phrase ``computer virus'' was invented by Fred Cohen, a PhD student at the University of Southern California, in 1983. He defined it as a program which could ``affect other computer programs by modifying them in such a way to include a (possible evolved) copy of itself''.
Three years later, The Brain virus was invented in Pakistan. It occupied all the unused space on a floppy disk, preventing its user from saving anything onto it.
The inventors of the virus were two brothers, Basit and Amjad Farooq Alvi, who left a text message inside giving details of their names, address and telephone number.
In December 1987, the Jerusalem virus appeared at Israel's Hebrew University. It was the first program which reinfected already contaminated files.
The next November, Robert Morris, 23, succeeded in unleashing a virus onto the US military's internet prototype, the Arpanet. Around 6,000 computers, including the Nasa research institute, were disabled by the virus which spread from one system to the next. The disruption resulted in losses of an estimated $96m.
Viruses now stopped being something only computer scientists talked about, but became the subjects of articles in Time, Newsweek and Fortune.
Media attention peaked in 1992 when it was predicted that the Michelangelo virus would bring giant computer systems to a standstill. In fact, few computers were affected.
Anti-virus programs fast became a profitable sector of the software market. Sales increased in 1999 when the Melissa virus caused $80m in damage.
Sam Roads, who helps run a JRR. Tolkien-themed Internet game which has 700 paying subscribers, says it is essential domestic computer users invest in such software. He said, ``The people who get hurt the most are the inexperienced.''