virtualbox.org

I'm running VB on a Windows Vista with a 3rd party firewall.
Is the traffic to my Guest machines monitored by the Host's firewall or do I need to install a firewall on my guest machines too?

Thank you very much!

Test it with angry ip scanner and such port scanning tools, never do guesswork with firewalling, test it.

You do for sure if you use Bridged. NAT traffic should be checked, but if you allow all connections by VB, it won't help.

Does your VM get a new IP from a router? Then yes, you need a firewall.