Optus inform me that 47% of my e-mails are spam and half of what...

Optus inform me that 47% of my e-mails are spam and half of what gets past I delete with Mailwasher, the virus Bloodhound was blocked by Nortons this morning, I feel like I'm under seige.
At least 5 this week notifing me my back account has been debited and to click on the link. (I didn't)

I've heard of people running a second computer as a hardware firewall, well I think that's what it does, can someone with knowledge of this give me a brief outline please?