If another computer on your network is infected with a worm/other malware, even with a physical router this malware can infect your computer. The best protection against this is using software firewalls and set "Untrust Network" and to turn off 1. Client for microsoft network and 2. file and printer sharing. This would make your computer super safe against that type of threat. (http://www.grc.com/su-fixit.htm) Another vulnerability comes from software exploits such as p2p connections. The best protection against this is to update your clients but in my opinion more importantly 1. run the software with sandboxie/sandboxed and 2) run the software under lua vs full admin rights. So this way even if my p2p client had an exploit, they could not do serious damage to my computer because the program is running LUA and sandboxed. Now when I am running VirtualBox with Bridged Networking, I really don't understand how this plays into the equation and if it would open more vulnerabilities: Q) if I were to run P2P with full admin rights on Virtualbox, would this make my host computer vulnerable? (I wouldn't be running P2P under sandboxie and no firewall in the VM). And would it open up any new vulnerabilities to network worms/malware? What I don't understand is if I am running VirtualBox under NAT and use P2P, I can see connections being made under VirtualBox on my firewall's active connection. And since Virtualbox is running with LUA, I feel confident and safe in this mode. However when I am running VirtualBox under Bridged Networking and use P2P, I can't see any connections being made on my firewall's active connection and I really dont' know where all the connections are being made and if they are under LUA protection so it worries me. Mrkvonic if you happen to see my thread and if its okay with you, you said that Bridged Networking "exposes machines to network with possible security implications." Are you talking about bridged networking putting my host at risk or just my guest vm? (http://www.dedoimedo.com/computers/virtualbox-network-sharing.html) If anyone knows, feel free to share your expertise and that includes you Mrkvonic, Thanks.