Trojans are all over the internet always trying to enter your system by bypassing your firewalls and the Antivirus softwares. At one time or another every ones system will definetly suffer the consequences of a Trojan Horses's attack.
The instant you click on the particular infected file thats the last thing you did not want to do but its already too late since its have done the what the Evil guy wants to do and finishes its mission of purpose.
So what is a Trojan basically they are not in truth a computer virus. But they are serious and need to be exterminated but these are not capable of copying themselves into multiple locations of our PC or copying to other systems in LAN or else moving to other computers.
Thes are some bad programs that is intended to cause some serious damage to your PC by stealing some of your inmportant informations that you have saved in your PC. They always disguise themselves and they use fake names or they get binded with another file that we normally use in our day to day life. By doind so they manage to get you to establish them on your Computer.
Even a technically sound person can fall foul of Trojans since it just need a moments lack of judgment and a little click of the mouse to cause so much trouble from our side that we often do.