Virus-Malicious programs intend to cause harm to targeted systems and include virus, worms, Trojan horses, Logic bombs and hoaxes[1].A virus[2] is a program that infects an

executable file and after infecting it causes the file to function in an unusual way. It propagates itself by attaching to executable files like application programs and operating system. Running the executable file may make new copies of the virus. On the other hand there are programs that can copy itself called worms which don’t alter or delete any file but only multiply itself and send the copy to other computers from the victim’s computer

[1] Different kinds of virus hoaxes

[2] Computer viruses are small software programs that are designed to spread from one computer to another and to interfere with computer operation.