Trojan Horse Virus - What is a Trojan Horse Virus
The majority of people are familiar with the story of the Trojan Horse. During the siege of Troy, the Greeks
left a large wooden horse outside the gates, supposedly as a peace offering. The Trojans took the horse inside the
city walls only to find it was full of Greek soldiers who quickly overrun the city. A Trojan Horse Virus or Trojan
Virus on a computer is very much the same. It looks like a harmless or useful program but in reality contains
concealed code that can wipe out data or install spyware.
A Trojan Virus is frequently referred to as a virus, but unlike a true computer virus, it does not duplicate
itself. It is purely designed to gain access to your computer system and wreak havoc, just like the legendary Greek
Most Trojan Horse Virus or Trojan Virus as it is more commonly known, are spyware and are used to monitor your
computer activity and send details to a third party without your knowledge or consent.
Spyware can be used to deliver unsolicited popup advertisments or to log personal details such as credit card
numbers and passwords, or even reroute your browser to a commercial site. The unscrupulous vendor at that site has
usually paid the spyware author to do just that.
Another common use for a Trojan virus is to install what is known as a 'backdoor'. This is an access point to
your computer which bypasses the normal login procedure. Hackers use backdoors to gain control of your computer to
send spam or to inflict damage to your data or operating system. Since the damage appears to originate from your
computer system it can be difficult to combat.
How a Trojan Horse Virus is Distributed
Trojans are concealed in programs which look as though they are useful. You visit a free utility site and
download one of these 'useful' programs and run it. Immediately, your computer system is infected without you even
A Trojan Horse Virus can also be spread through email attachments. If the attachment contains an executable
file, that file can also contain a Trojan virus which will infect your computer if the program is run.
Executable files have extensions such as .exe but on occasion the extensions are hidden to make the file look
like a harmless text file. An illustration of this would be a file named 'look_at_me.txt.exe. The user may not
notice the '.exe' part of the filename (the extension) and believe it to be just a text file. Some operating
systems allow users to hide extensions, so in this case the user would only see 'look_at_me.txt'.
Newer tactics include embedding trojans inside image files. The golden rule is to never open a file from an
unknown source, or when its arrival is unexpected. Even well meaning individuals pass on viruses this way without
It is common for Trojans to be spread through operating system vulnerabilities. An operating system, such as
Windows or Linux, controls the basic operating functions of the computer. Computers connect to the Internet through
'ports', some of which present security risks and Malware takes advantage of these vulnerabilities.
One of the more well known Trojans is called Sub7. Some claim it has genuine uses, such as remotely controlling
your own computer, though it is often used for more malicious activities. Computers with Sub7 installed are
accessible from a remote location and can be used to steal credit card numbers or passwords by logging keystrokes
Trojan Horse Virus Removal
Most, if not all, antivirus software will detect and remove Trojan Virus although a minority of antivirus
programs require you to manually scan attachments or other incoming files. However, it is advisable to get software
that does it automatically. It is also imperative to keep your virus database up to date to provide the best
protection. New virus variants come about all of the time
Always be on your guard when opening email attachments, even if they come from a known source. If the attachment
is from an unknown source, the best advice is not to open it unless you are 100% sure that it is safe to do so.