What is a Trojan?

A Trojan (Horse) is usually a harmless looking program containing what is mainly, but not always, malicious or harmful code. When a Trojan is run, it unloads any number of commands, scripts or hidden programs usually without the knowledge or consent of the user. Frequently used to get around your security measures in order to allow unauthorised access to your system.

Most infections occur because the user has been tricked or misled into running a program that is infected, often via an email with an attachment or a link in the body of the message but other methods are Instant Messages, infected CD's, USB flash drives and downloading from a website.

A few examples of the type of damage caused:-

• Erasing or overwriting data
• Unexpectedly shutting down your computer
• Logging keystrokes to steal passwords and credit card details
• Setting up networks of 'zombie' computers to send spam and Denial of Service(DoS) attacks
• Uploading/downloading files without permission
• Corrupting files
• Allowing unauthorised remote access to your system

Most Antivirus programs can delete Trojans quite easily, but if the Antivirus cannot find the trojan it is worth rebooting the computer in safe mode as this may allow the Antivirus to find and delete the Trojan.