Antivirus are small software programs that can spread from one computer even to another and to interfere by using computer operation.
A viral might.. corrupt or delete data on your computer, use your e-mail process to spread itself to be able to other computers, or even erase everything on the hard disk.
Antivirus are often spread just by attachments in e-mail emails or instant messaging communications. That is why it is necessary that you never open e-mail attachments unless you know who it’s from also, you are expecting it.