When the original Trojan Horse was gifted by the Greeks to the Trojans, it was accepted as a peace offering and taken into the city without a second thought. But, in the middle of the night, the Greek army hidden inside it attacked the unsuspecting Trojans and destroyed the city. Similar to the method used in this snippet of ancient history, the technological Trojan acts to destroy files in a computer after getting into it through seemingly harmless means.

The first Trojan attack in computing was found in 2002 ? it had infected SendMail and OpenSSH packages. A hacker had broken into the websites that did the distribution and switched the original, harmless files with the ones with the Trojan. This incident pointed out that it is very easy to get your computer infected through downloads. Now users try to tackle it by using the most sophisticated malware scanners before installing anything.

Another common way of spreading various Trojan Horse infections is email. Since people are naturally curious, the sender uses enticing file names to attract your attention and make you open the file. Other popular methods of spreading Trojan Horses are through instant messenger programs and shared files. One important fact to keep in mind is that a Trojan Horse can’t spread by itself. It needs the user to take action on the file, which means if you receive a Trojan and you click on it, it’ll spread. But, if you ignore it and remove it from your system, you have no problems.

The difference between a Trojan Horse and a virus is that viruses spread on their own through a network to other systems connected in the network. Trojan horses need to be transferred by the users and are not always harmful to the files on your system. They often provide unauthorized personnel with a back door to enter the affected computer without passing through any authentication procedure.

Trojan Horses are categorized into six types. Classified according to how they access and damage systems, these categories are remote access, data destruction, security software disabler, server Trojan, denial-of-service attack and downloader. Some common damages done by a Trojan malware can be all or any of the following ? corrupting files, erasing or overwriting data, encrypting files, copying fake links, allowing undetected remote access to your computer, spying, logging keystrokes (recording usernames, passwords, credit card numbers etc), email address harvesting, deactivating and interfering with valid programs and automatically shutting down and restarting the computer.

These malware types are usually undetectable, but ordinary anti-virus and anti-spyware programs are able to check, detect and remove Trojans under typical circumstances. If a problem arises when trying to remove a Trojan infection, it’ll be because the Trojan has binded with a legitimate file. In such cases, the computer has to be booted in safe mode or with the original operating system CD, before attempting to remove the Trojan.

To avoid infection by a Trojan Horse, the wisest thing to do is to never open files you have no reason to trust and to be very careful of what you download ? always scan before opening. Your malware scanners should always be updated scrupulously ? then they can get rid of any malware that might get into your computer.