Most viruses can also replicate themselves. All computer viruses are manmade. A simple virus that can make a copy of itself over and over again is relatively easy to produce. Even such a simple virus is dangerous because it will quickly use all available memory and bring the system to a halt. An even more dangerous type of virus is one capable of transmitting itself across networks and bypassing security systems.
Some people distinguish between general viruses and worms.
A worm is a special type of virus that can replicate itself and use memory, but cannot attach itself to other programs. A computing network connected over hundreds or thousands of miles, usually via telephone lines or radio waves. A subset of the Internet that uses images, multimedia elements, and hypertext navigation to communicate information globally. A connection of computers worldwide that host, serve, and transmit data among computer users. Using a Web browser ,, users can access the World Wide Web.