classification of virus

Types Of Virus

Trojan horse

A Trojan horse is a program designed as to seem to being or be doing one thing, such as a legitimate software, but actually being or doing another. They are not necessarily malicious programs but can be. A trojan horse can be used to set up a back door in a computer system so that the intruder can return later and gain access. Viruses that fool a user into downloading and/or executing them by pretending to be useful applications are also sometimes called trojan horses. (The name refers to the horse from the Trojan War, with conceptually similar function of deceiving defenders into bringing an intruder inside.)

Virus

A virus is a self-replicating program that spreads by inserting copies of itself into other executable code or documents. Thus, a computer virus behaves in a way similar to a biological virus, which spreads by inserting itself into living cells.

Worm

Like a virus, a worm is also a self-replicating program. The difference between a virus and a worm is that a worm does not create multiple copies of itself on one system: it propagates through computer networks. After the comparison between computer viruses and biological viruses, the obvious comparison here is to a bacterium. Many people conflate the terms "virus" and "worm", using them both to describe any self-propagating program. It is possible for a program to have the blunt characteristics of both a worm and a virus.

Key loggers

Key loggers are used by hackers to spy on a target computer or system by recording the keys pressed by users, thereby capturing useful information such as passwords when they are typed by users. Key loggers can also be used for safety, such as when police forces use them to spy on chat rooms and enable them to find pedophiles.