Vyatta is a Linux-based routing and security distribution. It is meant to deliver a flexible, affordable alternative to Cisco 1800 through 7200 series routers. Vyatta is also a great virtual router, virtual firewall, virtual security solution for VMware, Xen, XenServer, and KVM virtualization projects.
Zorp is a proxy firewall suite with its core architecture is built around today's security demands: it uses application level proxies, is modular and component based, uses a script language to describe policy decisions, makes it possible to monitor encrypted traffic, lets you override client actions, and lets you protect your servers with its built in IDS capabilities.
eurephia is an authentication plug-in for OpenVPN. It enhances the OpenVPN authentication process by using user name and password authentication in addition to SSL certificates. If too many failed attempts are registered, the user account and/or IP address will be blocked. For Linux servers, iptables support is also included, which can be used to restrict each user's network access through the VPN channel. OpenVPN 2.2 or later is required.
ipt_pkd is an iptables extension implementing port knock detection with SPA (single packet authorization). This project provides 3 parts: the kernel module ipt_pkd, the iptables user space module libipt_pkd.so, and a user space client knock program. For the knock packet, it uses a UDP packet sent to a random port that contains a SHA-256 of a timestamp, small header, random bytes, and a shared key. ipt_pkd checks the time window of the packet and does the SHA-256 to verify the packet. The shared key is never sent.