OpenSnitch is a GNU/Linux port of the Little Snitch firewall
Anti Spam SMTP Gateway
Free UTM appliance: firewall, VPN, WAF and antivirus in one ISO.
One of the most advanced DNS Proxy and DNS Firewall in one product.
Powerfull Web Application Firewall for PHP
Webinterface to (un)ban IPs in Fail2Ban
Detect Flooder IPs, Reduce Attack Surface against HTTP Flood Attacks