Use caution when receiving attachments from strangers or even friends or family. The attachment could contain a virus unknowingly. Be on the safe side and scan incoming attachments before executing them. Download with care. Only download files from Web sites you can trust.
Some sites guarantee that their files are virus free.
If you are unsure, it's best to steer clear. Store these backups in a safe place, separate from your hard drive. Get virus software. There are over 10,000 computer viruses, but there is software out there to slay those nasty viruses. These anti-virus programs are not perfect, but they're your best bet for survival.