**4.7 Trojans**

Trojans are programs that appear as perfectly genuine but, in reality, have a malicious part embedded in it. Trojans are spread usually through email attachment from the trustworthy contacts and also on clicking on fake advertisements. The payload of Trojans is an executable file that will install a server program on the victim's system by opening a port and always listening to that port whereas the server is run on the attacker's system. Hence, whenever the attacker wants to login to the victim machine, they can do so by means of the backdoor entry making it hidden from the user.
