Open Source C Firewall Software

Smoothwall is a best-of-breed Internet firewall/router, designed to run on commodity hardware and to provide an easy-to-use administration interface to those using it. Built using open source and Free software, it's distributed under the GNU Public License.

VTun is the easiest way to create Virtual Tunnels over TCP/IP networks with traffic shaping, compression, and encryption. It supports IP, Ethernet, PPP and other tunnel types. VTun is easily and highly configurable. VPN, Mobile IP, Shaping, etc

Privoxy is a non-caching web proxy with advanced filtering capabilities for enhancing privacy, modifying web page data and HTTP headers, controlling access, and removing ads and other obnoxious Internet junk. Privoxy has a flexible configuration and can be customized to suit individual needs and tastes. It has application for both stand-alone systems and multi-user networks.

The IPCop Firewall is a Linux firewall distribution. It is geared towards home and SOHO users. The IPCop web-interface is very user-friendly and makes usage easy.

Advanced Onion Router is a portable client for the OR network and is intended to be an improved alternative for Tor+Vidalia+Privoxy bundle for Windows users. Some of the improvements include UNICODE paths, support for HTTP and HTTPS proxy protocols on the same Socks4/Socks5 port with HTTP header filtering that generates fake identity-dependent headers every time the identity is changed (proxy chains are also supported), support for NTLM proxies, a User Interface that makes Tor's options and actions more accessible, local banlist for forbidden addresses, private identity isolation, a point-and-click process interceptor that can redirect connections from programs that don't support proxies, also giving them fake information about the local system and support for .onion addresses. Also, it can estimate AS paths for all circuits and prevent AS path intersections, it can restrict circuits to be built using only nodes from different countries, can change circuit lengths and more.

simplewall is an open-source Windows application that provides a user-friendly firewall control interface powered by Windows Filtering Platform (WFP), enabling users to block or allow outgoing and incoming network connections without diving into complex OS settings or command-line tools. The app presents a clean, intuitive UI where users can define rules based on process names, IP addresses, ports, and protocols, making it possible to restrict apps from accessing the internet or control specific traffic flows with fine granularity. Because simplewall leverages WFP directly, it operates at a low level in the network stack, ensuring reliable enforcement of rules system-wide while remaining lightweight. It also includes optional modes like blocking all inbound or outbound traffic except what’s explicitly allowed, and supports temporary rule application, logging, and diagnostic views to help users understand what traffic is being blocked or permitted.

CacheGuard Gateway is a free and open-source Unified Threat Management (UTM) solution, a Web Application Firewall (WAF), and a Quality of Service (QoS) platform designed to optimize WAN traffic. To obtain a CacheGuard Gateway appliance, download CacheGuard-OS and install it on the bare-metal or virtual machine of your choice. It’s that simple and completely free. The UTM includes a firewall, web antivirus, VPN server, and a URL-filtering and SSL-inspection web proxy. The WAF operates in conjunction with a reverse proxy, web application load balancer, and SSL offloader, and is capable of blocking malicious requests as well as traffic from IP addresses with poor reputations. The QoS manager enables traffic shaping to prioritize critical network flows, load balance multiple WAN links, and cache web traffic.

SS5 is a socks server for Linux, Solaris and FreeBSD environment, that implements the SOCKS v4 and v5 protocol.

Endian Firewall Community (EFW) is a "turn-key" linux security distribution that makes your system a full featured security appliance with Unified Threat Management (UTM) functionalities. The software has been designed for the best usability: very easy to install, use and manage and still greatly flexible. The feature suite includes stateful packet inspection firewall, application-level proxies for various protocols (HTTP, FTP, POP3, SMTP) with antivirus support, virus and spam-filtering for email traffic (POP and SMTP), content filtering of Web traffic and a "hassle free" VPN solution (based on both OpenVPN and IPsec).

Firewall Builder is a GUI firewall management application for iptables, PF, Cisco ASA/PIX/FWSM, Cisco router ACL and more. Firewall configuration data is stored in a central file that can scale to hundreds of firewalls managed from a single UI. A message from project maintainers: After working on Firewall Builder for many years it is with some sadness that Vadim and I are announcing that we have suspended all development activity for this project. Firewall Builder has been a great project to work on and we have truly appreciated all the support and positive feedback that the user community has provided. Without you we wouldn’t have been able to keep things going this long. You might be wondering why we are doing this... We had an exciting opportunity come up to start a company developing advanced security automation solutions. This was a chance of a lifetime that we just couldn’t pass up and unfortunately it means that we no longer have time available to work on improv

PeerGuardian is a privacy oriented firewall application. It blocks connections to and from hosts specified in huge blocklists (thousands or millions of IP ranges). Its origin seeds in targeting aggressive IPs while you use P2P. PeerGuardian Linux: Not developed actively anymore. Team might still be around. Some unreleased changes on git. Outdated technology. Peerguardian OS X: Not developed anymore. We've lost contact with the OS X developer. PeerGuardian Windows: Not developed anymore. It's highly recommended to use PeerBlock instead, which is a continuation of PeerGuardian's development in Windows, with bug fixes and support for Windows Vista and Windows 7. Collaboration with peerblock.com is welcome! PeerGuardian is an open project. Not only is its source code open for you to read, use, and modify - but the project is open for you to join and contribute in any form (code, documentation, bug reports, web and support).

Siproxd is a proxy/masquerading daemon for the SIP protocol. It allows SIP clients (softphones & hardphones) to work behind an IP masquerading firewall or router.

SSHGuard protects hosts from brute-force attacks against SSH and other services. It aggregates system logs and blocks repeat offenders using several firewall backends, including iptables, ipfw, and pf.

BrazilFW is a mini Linux distribution designed to be used as a Firewall and Router that runs easily on older computers. An old PC running BrazilFW is much more powerful and efficient than commercial software for routing in offices and residences running on a "powerful" computer. BrazilFW is based on Coyote Linux, which was designed by Joshua Jackson who discontinued Coyote Linux in version 2.24 in August 2005. In that same month comes on the scene BrazilFW Firewall and Router (BFW) with version 2.24, which is led by "Claudio" and "Marcelo - Brazil", running only on floppy disks, and being 2.30.1 the last version with this support . The following versions, as well having automatic detection of network cards, only run on large capacity media, such as hard disk (HD). Versions in Development: * 2.33.x: Uses kernel 2.4.x and is developed by Marcinho Samurai. * 3.x: Uses kernel 4.x and is developed by WoshMan

Those who have read past the "Malware" warning can be assured there is absolutely no malware in this OS or in the download. This warning comes from the "netcat" binary included in the download as a DOS time client. Unfortunately netcat has code that is flagged as malware. FREESCO, a NAT/firewall router/server based on Linux and runs on a single 1.44MB floppy. Freesco is very powerful and versatile and can connect multiple home or small office networks to most types of Internet connections including dialup.

wipfw - IPv4 packet filter and traffic shaper for Windows based on IPFW (FreeBSD firewall).

Netdeep Secure is a Linux distribution with focus on network security. Is a Next Generation Open Source Firewall, which provides virtually all perimeter security features that your company may need. It offers Web content filters, ensuring better performance of the network, allowing users to use the service efficiently and securely, providing a deep control of the use of the Web access service, blocking access to unwanted websites, Virus, Spam, Applications and intrusion attempts. Its configuration is made entirely by the web interface.

The WiFi Guard Dog project is a complete and embeddable captive portal solution for wireless community groups or individuals who wish to open free HotSpots while preventing abuse of their connection. Go to dev.wifidog.org to download the latest version.

Bypass is an IP forwarding/tunneling tool which can be used where limited bypassing of a firewall is necessary, but relaxing the restrictions in the actual firewall is not an option. The aim is for bypass to be automatic and transparent.

ModSecurity is a web application firewall that can work either embedded or as a reverse proxy. It provides protection from a range of attacks against web applications and allows for HTTP traffic monitoring, logging and real-time analysis.

A Free SOCKS proxy server for Linux, macos and FreeBSD

VTD-XML is the next generation XML parser/indexer/editor/slicer/assembler/xpath-engine that goes beyond DOM, SAX and PULL in performance, memory usage, and ease of use.

The Nemesis Project is designed to be a command line based, portable human IP stack for UNIX-like and Windows systems. The suite is broken down by protocol, and should allow for useful scripting of injected packets from simple shell scripts.

The goal of FireStarter is to provide easy to use, yet powerful, graphical tools for setting up, administrating and monitoring firewalls for Linux machines.

Blocks "known bad" IP-addresses from accessing your machine, especially corporate/governmental agencies. This is a fork of PeerGuardian 2, fixing various Vista/Win7 problems.