Virtualbox virus protection?

OK, once I got the correct version (which is a bug fix for problems caused by anti-virus programs) I've managed to set up a virtual XP machine with the software I want to use and a printer driver, and got it activated. Can't actually find the files I've previously created with this program, which is a bit annoying, but I really only need to re-create one, everything else will be new.

Question - while I'm not planning to use this for internet access, I may end up needing to do so. Does it have any anti-virus protection from the software that's already installed under Windows 7, or do I need to add something?

While I could RTFM, it's 300+ pages and I'm hoping someone may already know!

later - asked several places, apparently there is a small chance of a virus infecting the virtual machine, but very little of it infecting anything else before it gets taken out by my anti-virus software. Since this will probably only be used for a few hours a year, and I don't really plan on using the browser at all, I think it's an acceptable risk.

later still - on reflection I've installed Avast in the virtual PC - no reason not to, and I might as well have the extra protection.