A computer Trojan Horse (or Trojans for short) is a piece of software that works in a concealed manner so that you may think it is doing one thing when in reality it is doing another.

History of the Trojan Horse
A Trojan Horse derives its name from the Trojan War. Legend has it that King Odysseus built a Trojan Horse as a gift to the city of Troy to signify surrender. He then ordered the Greek army to retreat and left the ‘gift’ outside the city gates. However it turned out that the Horse had more than 40 soldiers hidden in its belly. Once inside the city of Troy, these soldiers snuck out and opened the gates for their fellow soldiers who went on to attack the unsuspecting city with iron weapons.

A Trojan Horse is not a virus

It is important to note that a Trojan Horse is not a virus. It does not replicate itself as viruses do. While it may sometimes be destructive, it may also be useful for example when you need to administer your server remotely. However most Trojans are designed to be malicious and hence the wrongly used term Trojan Horse virus.

What does a Trojan Horse do?

Non-malicious Trojan Horse programs are used for remote access, remote managing, security software, Denial-of-service attack (DoS) and forensics.

Malicious Trojan Horses work by gaining remote access to your machine and performing a harmful task. Trojans can be used to get your personal information such as your passwords, credit card numbers and other information stored on your computer. They can also be used to spy on you, to delete or change certain files or to direct you to certain sites or send mails to people in your address book. They can also be used to damage your hardware.

Most attackers know that it may be easy to discover a virus that is making its rounds from it’s name. They will therefore try to achieve the same task by hiding it in another program that you think is useful when, in reality, it is not. The Trojan Horse camouflages itself so that it appears like a part of the system and hence you continue with your activities unaware of the malicious code’s presence. Since the attackers want to get some sort of control over your machine, they may even go as far as naming Trojans with crucial Windows’ file names or hiding the Trojans in free software such as games or music.

How do I get rid of Trojans?

If you find that you have been infected with a Trojan Horse, make sure you disconnect from the Internet. Then look for a suitable Trojan scanner program and use it to scan your machine. If Trojans are detected, use the program to delete the Trojans. Unlike viruses which infect legitimate files and need to be cleaned, Trojans cannot be cleaned and hence need to be deleted.

How do I avoid getting infected by Trojans?

1. DO NOT download files blindly from people or sites which you aren’t sure about.

2. Watch out for hidden file extensions! Trojans are normally executable files with a .exe extension. That does not mean that if you avoid using an exe file then you will be safe. Most attackers are aware of this and therefore try to hide the name of the file so that one does not immediately realize what type of file they are using. It does help to unhide your extensions so as to clearly see what files you are using. Note that only the last extension counts, so a file with the name beautifulwomen.txt.exe is not a text file but an executable file.

3. DO NOT think you are completely safe just because you run anti-virus programs. Some anti-virus programs do not detect Trojans simply because they were not designed to do that.

4. DO NOT follow unsolicited links or open attachments in e-mail messages that you did not ask for.

5. Use an Internet firewall.

For more information on the Trojan Horse Virus read What is a Trojan Horse

http://www.tech-faq.com/trojan-horse-virus.shtml

http://www.rolo.org/trojan-horse-viruses.html