SonicWall - SonicWall security solutions protects your network, systems, users and data from cyber threats.
NethServer - NethServer is an operating system for Linux enthusiasts, designed for small offices and medium...
Comodo Firewall - Comodo Firewall Pro - Secure your system against internal attacks such as Trojan viruses /...
ClearOS - A very good alternative for Windows Server, for free
Emsisoft Online Armor Firewall - Emsisoft Online Armor Firewall is a freemium online firewall protection system by the Emsisoft that is based on the own independent protection technology of the Emsisoft.
Univention Corporate Server - Univention Corporate Server UCS with Active Directory functions and App Center is the cost-efficient and popular successor to Microsoft's server solutions.