Antivirus are small software programs that can spread from one computer to a new and to interfere by using computer operation.
A virus might.. corrupt or delete data on your hard disk, use your e-mail method to spread itself to be able to other computers, or even erase everything onto your hard disk.
Antivirus are often spread simply by attachments in e-mail messages or instant messaging email. That is why it is crucial that you never open e-mail attachments unless you know who it’s from and you just are expecting it.