Using a virtual machine to access the internet

I am becoming tired with all these security problems with XP. Suppose one uses a virtual machine (VMware, or other), with Windows XP as host OS and, say Ubuntu as guest OS, is it possible to block all internet activity on the host OS (XP), and at the same time allow internet access to the guest OS? If yes, then a step by step explanation how to do it would be very much appreciated. Thank you.