What is a computer trojan?

Mostly people confuse the term computer Trojan with computer virus. They think that both of these are same. No doubt they both infect your computer but they both have slightly different characteristics. Trojan is a malicious program that cannot replicate itself like the computer virus but can cause serious security problems. It appears as a useful program but in reality it has a secret code that can easily access your system.

Trojan got its name after ancient Trojans.
During Siege of Troy ancient Trojans believed that the large wooden horse left behind by the Greeks outside the gates was a sign that after years of war they now wanted peace because the Greeks were losing the war. The Trojans accepted that gift and brought it inside their city. The Greek soldiers were inside that horse. During night they opened the main door so that more soldiers could come inside the city and they could easily attack on the Trojans. Similarly a computer Trojan appears something else but in reality it harms your system.

1)It creates backdoor to your computer which allows the hacker to do anything on your system or we can say that the hacker will get control on your system without your permission. He can see your e-mails, record keystrokes, access password protected accounts and can get any type of information about your computer.

2)It can do malicious functions like rebooting your computer or deleting files.

3)It also installs spyware which takes you to the unwanted sites.

4)Some annoying Trojans can change desktop or add silly active desktop icons.


Hidden in programs
They remain hidden in the programs that appear useful because when you download a program from a site you think that this program will be useful but instead it contains Trojan. When you run that program your computer gets infected.

Through e-mails
Trojans also spread through e-mails. Attacker sends you an email attachment which has executable file. When you open that attachment the Trojan inside it will infect your system. For e.g.:- there is a file “cool_girls.txt.exe”. “txt” shows that it is a text file and “exe” shows that this executable file has the extension. Sometimes you may not notice about “exe” and take it as only a text file. When you open this file your system gets infected. Some users use the operating system that even allows hiding these extensions so that the file appears a harmless file and it will look as “cool_girls.txt”

By sending or receiving files from an unknown person on MSN, yahoo messenger, AIM etc may infect your system with Trojans.

Image files
Another tactics of spreading Trojan is by embedding it in some image files. Do not open an image file from an unknown person or even from known person when the arrival of file is unexpected.

Operating system vulnerabilities
It also spreads through operating system vulnerabilities because some
Parts that connect computer to the internet have security risk.


1)Almost all antivirus software and some antispyware programs can detect and remove the Trojan. Always keep your antivirus up to date for better protection. If no Trojan is found even after the scan and you still think that your system is infected by a Trojan then you can verify this from an expert.

2)Do not download anything from unknown person or suspected site about which you are not 100% sure.

3)Always use caution while opening an email attachment even it is from a known person.

4)Do not receive files during the chat from an unknown source.

5)Firewalls will also protect your computer from Trojan because it looks over the open ports of your system for incoming data. It will either block or let it pass according to the choice of user.

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    Had a trojan yesterday 3-15.I worked all day trying to get rid of that thing.Finally this morning I was running a full scan on my computer and the anti-virus I run microsoft security Essentials told me out of the blue that a trojan had been encounted on my computer and I removed it.Now everythings back to nomal.Thank God, Its been a nightmare.

    a trojan attacked my daughters computer yesterday, we worked several hours last night.

    I had just bought Norton Utilities and installed it on the computer a few weeks ago. Norton finds it and reports that all threats have been resolved. However the trojan keeps attacking over and over. I also installed Spyware Doctor but it didn’t even detect the trojan.

    Will this trojan keep attacking or is Norton not the right program to get rid of it?

    thanx ur info is really usefull n up to date i had a trojan in my pc i tried a lot to sort out the problem but coudn’t do it.nw i hav figured it out and removed it.thanx alot

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