Computer viruses existed long before the popularization of the Internet, But they can now proliferate fare more rapidly in the connected world. There are actually three types of infectious programs which are following :—
- Trojan Horses
A computer virus is a remarkable analogy of its biological counterpart like bio-virus, computer viruses are not alive in the sense that a computer virus must first infect a normal program before its code can be run. A bio virus must infect a cell before it van hijack the DNA replication in the cell to create copies of itself. Once a computer virus’s has infected a program, the next time the program runs, the virus payload will be activated. Typically a virus will try to copy itself to other programs, or across the network, but most also contain some form of harmful instructions like delete files, format drives etc.
A computer worm, on the other hand, is usually a fully functional program that depends exclusively on network for its reproduction. the MS Blaster worm that attacked, and continues to attack, Microsoft windows installations is an example of such a worm.
Trojan Horses :—-
Finally, a Trojan horse is a program that looks normal but that carries a terrible payload. Some Trojan horses may masquerade as cute little dancing frogs on the screen, or whatever . Other may set up a screen that looks exactly like the normal window login screen and as soon as you type your user name and password, the Trojan horse sends that information off to someone on the internet and the pops then pops up the regular login screen.
So, these are some important virus which are mostly used by hacker . If you have some questions about this topic then write in comment box….