Introduction To Antivirus: Trojan Horse

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26 Jan

A guide to different virus types including viruses, worms and Trojans. Compare the best antivirus programs at software.com.

So, one day your anti-virus program, say Kaspersky or Norton, alerts you that a threat to your computer has been neutralized. Furthermore, you learn that this threat was a malicious remote access Trojan horse that you had unwittingly executed, thinking the program was just a new update for your computer.

You're relieved to know that the threat is neutralized, but that leaves you pondering, "What is a Trojan horse, and how does it differ from a worm or a virus?" Although these three malware terms are often used interchangeably, there are subtle differences that make each distinct and which when understood can help you better protect your computer.

Viruses are programs that attach themselves to another file, replicate, and then spread unknowingly. Their effects can range from annoying (displaying messages) to malicious (deleting large sections of your hard drive). Most viruses are attached to an executable file, like an email attachment, and will only become malignant once opened. After that they are able to replicate themselves and spread. At each new computer encountered, the virus must once again be opened before it can cause damage. Some well known examples are Melissa, which sent itself to the first 50 addresses in the user's address book, clogging networks and crashing servers around the world, and the Love Bug, which sent itself to everyone in the user's address book AND destroyed media files while it was at it.

Worms are a sub-category of virus that technically causes no harm to your computer. The majority of worms copy and send themselves through your email or network to everyone possible. Unlike viruses, they do not need to be opened, and can spread without any human intervention. They can cause massive damage not because they attack your computer, but because these exponential replications can quickly crash a network if not stopped. Some worms also carry a payload, defined as a damaging program directed at the computer itself. An example is the Blaster Worm, which not only caused networks to crash, but also severely hampered individual computers ability to access the Internet.

Trojan horses, like the story from which they come, are stealth viruses. A Trojan will typically enter your system by disguising itself as a friendly program until executed, whereupon it will become malicious. Unlike viruses and worms, the Trojans cannot replicate themselves and must be spread through the exchange of the programs to which they are attached. They attack computers rather than networks, and have been known to do everything from deleting files to creating backdoors, points of easy access which allows hackers to access the files on your computer remotely. An example of a Trojan horse is SpySheriff, which masquerades as an anti-spyware program and also as virus protection software but when executed essentially takes over a user's computer, preventing access to files and the internet. With the threat of new malware being a constant concern, it can be hard to know how to protect your computer. Here are three tips for keeping it healthy:

• Install a good firewall program and update it frequently.
• Don't open emails from unknown addresses. If you think its suspicious, it probably is.
• Before downloading a program, check it against a list of known threats; most antivirus programs have this feature.

Finally, make sure you have the best security possible by taking a look at the latest antivirus software and security suites. The quality of security products can change from year-to-year, so just because you have always used one product doesn't mean you should stick with it.

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