Quote Originally Posted by hgibbonsprt View Post
A computer virus is a program that is maliciously downloaded (usually through an URL or link attachment) onto your computer without your knowledge
No, that's a trojan.

can replicate/copy itself that can crash your entire system.
A properly written virus does not crash your system. The whole purpose of it's existance is propagation and avoiding detection. Crashing a system would certainly indicate something is wrong and would only attract attention.

A virus is self-replicating code that needs other executables to attach itself to. A worm is self-contained, self-replicating code.