Unfortunately there are people who seek to disrupt the use of computers with a variety of programs that are able to infect computers and subsequently damage them in some way.

These malicious programs range in effect from the mildly irritating to severely damaging. Computer operation is interfered with, data is deleted, recorded or corrupted, movement of the infection often rapidly spreading by the use of the internet.

Assaults on our computers often display the weaknesses in our security. Attacks such as these also highlight the degree to which we have all become interconnected and more sophisticated technologically.

Of the wide variety of computer infections in existence four characteristic varieties occur:

-Trojan horse: a computer program that masquerades as being able to perform a certain (usually benign or useful) task but that actually performs a different and damaging action e.g. erasing your hard drive or allowing open access to your computer. Once you click to use the program it downloads and your computer is suddenly infected.

-Viruses: these software programs attach themselves to specific programs. When these particular programs run, so does the virus, the result typically that your computer has been damaged in some way.

-E-mail viruses: these viruses are transported between computers via e-mail messages. Replication is achieved usually by this virus automatically e-mailing its self to most if not all of the e-mail addresses on the host computer.

-Worms: computer networks and the particular weak spots in their defenses are exploited by this electronic infection in order to propagate its self. A copy of this worm is able to scan the whole network for other computers with similar security holes through which it can then move to another computer for duplication.

Amongst the many cases of highly successful electronic infections a few notable ones have occurred. One of the best known was:

Code Red worm. This worm was released to devastating effect on the 19th of July 2001. In the space of 9 hours the worm duplicated its self onto new computers over 250,000 times. This worm replicated its self during the initial 20 days of each month, replaced infected servers with web pages displaying "Hacked by Chinese", and continuously targeted the White House Web server aiming to slow it or shut their website down. After a computer had become infected a wait of about an hour occurred, after which 100 connections would be attempted to port number 80 of the www.whitehouse.gov website (IP number 198.137.240.91). The US government responded by modifying the IP address and spreading the word about the Code Red worm. As with many infections, strains have appeared over time. Since this is a well known infection it has been monitored very closely with patches being freely available on the internet with which to combat the new strains.

Other major malicious programs from the past have been the "Slammer worm" from January 2003, "Mydoom worm" (January 2004), the "ILOVEYOU" (2000) and "Melissa" viruses.

So as not to become yet another statistic during the next major computer infection outbreak what is imperative is that you frequently update your computer with the latest antivirus tools and patches, read about current threats and follow basic preventative protocol regarding the opening of attachments and downloading of files.

If your computer does become infected the most important aspect to focus in on first is to target it specifically so that it is unable to spread to any more computers.