User`s guide

Trojan
A destructive program that masquerades as a benign application. Unlike
viruses, Trojan horses do not replicate themselves but they can be just as
destructive. One of the most insidious types of Trojan horse is a program that
claims to rid your computer of viruses but instead introduces viruses onto
your computer.
The term comes from a story in Homer's Iliad, in which the Greeks give a
giant wooden horse to their foes, the Trojans, ostensibly as a peace offering.
But after the Trojans drag the horse inside their city walls, Greek soldiers
sneak out of the horse's hollow belly and open the city gates, allowing their
compatriots to pour in and capture Troy.
Virus
A program or piece of code that is loaded onto your computer without your
knowledge and runs against your will. Most viruses can also replicate
themselves. All computer viruses are manmade. A simple virus that can copy
itself over and over again is relatively easy to produce. Even such a simple
virus is dangerous because it will quickly use all available memory and bring
the system to a halt. An even more dangerous type of virus is one capable
of transmitting itself across networks and bypassing security systems.
Worm
A program that propagates itself over a network, reproducing itself as it goes.
It cannot attach itself to other programs.
Types of Malicious Software
58
BitDefender Antivirus for Mac