How do bug spread out?

A computer system infection is a type of harmful code or program that, when executed, duplicates itself by modifying other computer programs and inserting its own code. When this duplication succeeds, the impacted areas are then said to be contaminated with a virus.

Infections often spread by developing a copy of themselves on a user's computer without the user's knowledge or permission. In many cases, viruses will be spread by e-mail accessories or by files shared on peer-to-peer networks. Once a virus has infected a computer, it can spread to other computer systems on the same network.

Some viruses are set to spread themselves in such a way that might cause major damage to a computer system. An infection may delete files, fill a hard drive with ineffective information, or corrupt system files. In some cases, an infection might even show a message or image that is designed to terrify the user.

Most infections are reasonably safe, and only trigger minor inconvenience to the user.  https://cleardex.io/?p=706 Some viruses can be really harmful, and can cause prevalent damage to computer systems.