what is a computer virus?

A virus is a program that replicates itself. It spreads by making copies of itself on a computer or by inserting computer code into program or operating system files. Viruses don't always damage files or computers, but they usually affect a computer's performance and stability. For a virus to infect a computer or to spread, you usually have to do something, such as open an infected e‑mail attachment.

How do i block virus?

Install an antivirus program. To be most effective, an antivirus program should always be turned on, should scan incoming e‑mail, and should scan file access.