A Trojan horse is a program that claims to rid your computer of viruses but instead introduces viruses into the system. Since they look like sincere programs they are referred as Trojan like the Trojan horse of Greek mythology. The Trojan program does not attach itself to the files like a virus nor replicate itself like a worm but it does provide unauthorized access to user’s computer.
They are mostly spread through internet downloads and online gaming programs. They mostly affect the targeted computers. The trojan program prompts you to do the normal functions such as inputting your email address or profile name. You do so, not knowing that, you have provided access to the malicious software. This software is capable of taking over the functionality of your computer. An infected computer will begin to operate slowly and will exhibit pop-ups from time to time. Eventually the computer will cease to operate, or crash.
The best way to avoid the Trojans is to adopt safe download practices. If you are not sure of the website safety, then it is probably best not to download any program from that source.
An example of the Trojan horse was “I love you” which infected several computers in USA and Asia, completely damaging the data of millions of computers