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Viruses and trojans what’s the difference

Trojan Horse: Normally shortened to just “Trojan”, they used to be a program that either pretended to have, or was described as having, a set of useful or desirable features, but actually contains a damaging payload. However now Trojans will be programs that open systems up to hackers by stealth, creating ‘open doors’ for them to gain control of the systems.

Virus (plural viruses): A software program that self-replicates (creates copies of itself). Viruses may damage or destroy data, cause the computer to crash, display messages, either immediately or on a specified date. Normally require human intervention in running a program or opening an email attachment. The notable exception being boot sector viruses, which are spread via disks simply being ‘booted up’.

Worm: A program that is designed to copy itself from one computer to another over a network, including the Internet itself. Can be spread by e-mail, IRC chat or copy themselves over the Internet as an open system is found. Because the worm doesn’t need human intervention, worms spread much more rapidly than computer viruses.

It would be easy to find fault with these simple definitions, and the way they operate, and what they do, are becoming increasingly blurred. The point is however, they are going to be around for a while.

So which is the worst? Simply whichever one your computer contracts! With the increasing sophistication of what is generically termed ‘malware’, not running anti-virus software is almost suicidal. It is also not good enough to buy the software, load it, and forget it. AV software that is not kept up to date (a minimum of once a week at the moment), is almost worse than none at all, since it engenders a false sense of security. It is also a good idea to subscribe to new virus warning services from your anti-virus software vendor.

One side effect of the tremendous upsurge in malware, is that as newly produced worms look for computers and Web Servers to infect, the enormous amount of Internet activity generated, actually slows down the Internet for everyone else. If you have a firewall running, all those attempts to communicate with HTTP or port 80 (amounts to same thing), are probably worms attempting to find a server running Microsoft’s Web Server software, so they can infect it.

For details of the most recent threats, go to our Virus News page. For software to help prevent or deal with threats, go to our Shop.

Paul Wood

Website design and maintenance

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