In information security , computer virus is a manmade program or piece of code that is loaded onto your computer without your knowledge and runs against your wishes. From behavior computer virus in a way is a similar biological virus which pervasions by inserting itself into living cells. Cell by cell and all organisms (computer) is ridden virus cells.
Without computer viruses there are separated two other types of malicious computer programs - viruses.

Trojan Horses

As already from this virus type name we can imagine, Trojan horses are programs that pretend to be legitimate software, but actually carry out hidden, harmful functions. Trojans can’t replicate themselves that mean, they can’t expand so fast as other virus types. But often they work together with viruses.

Worms

Worms are similar to viruses but do not need a carrier program or document. Worms simply create exact copies..

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