From a server prospective I am running windows defender on a Windows 2008 Server. I actually called my host, Server Intellect, and spoke with the level 3 techs. From a windows perspective and theirs it runs very well, low resources and keeps the systems clean. As for firewall I use the windows firewall with IPSEC to block specific ips. I pretty much block out most of the foreign countries that have bad spam and other malicious stuff. It really stops quite a bit of stuff.