A firewall is a system designed to prevent unauthorized access to or from a private network (which could be just one machine). Firewalls can be implemented in only hardware or software, or a combination of both. Firewalls are frequently used to prevent unauthorized Internet users from accessing private networks connected to the Internet, especially intranets. All messages entering or leaving the intranet pass through the firewall, which examines each message and allows, proxys, or denies the traffic based on specified security criteria.
There is a nice list of firewalls here.
There are many posts on the forums about different firewall apps and scripts so here they all are condensed into one page - please add your comments about each firewall, especially ease of use and a security check at Shields Up.
The Linux kernel itself has very powerful firewall called iptables. Other firewalls are usually just front-ends.
See the iptables article for more information.
- Simple stateful firewall
- man iptables http://unixhelp.ed.ac.uk/CGI/man-cgi?iptables+8
Arno's IPTABLES Firewall Script is a secure firewall for both single and multi-homed machines.
- EASY to configure and highly customizable
- daemon script included
- a filter script that makes your firewall log more readable
- NAT and SNAT
- port forwarding
- ADSL ethernet modems with both static and dynamically assigned IPs
- MAC address filtering
- stealth port scan detection
- DMZ and DMZ-2-LAN forwarding
- protection against SYN/ICMP flooding
- extensive user definable logging with rate limiting to prevent log flooding
- all IP protocols and VPNs such as IPsec
- plugin support to add extra features.
ferm (which stands for "For Easy Rule Making") is a tool to maintain complex firewalls, without having the trouble to rewrite the complex rules over and over again. ferm allows the entire firewall rule set to be stored in a separate file, and to be loaded with one command. The firewall configuration resembles structured programming-like language, which can contain levels and lists.
FireHOL is a language to express firewalling rules, not just a script that produces some kind of a firewall. It makes building even sophisticated firewalls easy - the way you want it. The result is actually iptables rules.
Firetable is an iptables-based firewall with "human readable" syntax.
AUR.AUR is available in the
The Shoreline Firewall, more commonly known as "Shorewall", is high-level tool for configuring Netfilter. You describe your firewall/gateway requirements using entries in a set of configuration files. Shorewall reads those configuration files and with the help of the iptables utility, Shorewall configures Netfilter to match your requirements. Shorewall can be used on a dedicated firewall system, a multi-function gateway/router/server or on a standalone GNU/Linux system. Shorewall does not use Netfilter's ipchains compatibility mode and can thus take advantage of Netfilter's connection state tracking capabilities.
ufw (uncomplicated firewall) is a simple front-end for iptables and is available in the official repositories.
See Uncomplicated Firewall for more information.
Vuurmuur Vuurmuur is a powerful firewall manager built on top of iptables. It has a simple and easy to learn configuration that allows both simple and complex configurations. The configuration can be fully configured through an GUI, which allows secure remote administration through SSH or on the console. Vuurmuur supports traffic shaping, has powerful monitoring features, which allow the administrator to look at the logs, connections and bandwidth usage in realtime.
AUR.AUR is available in the
Firestarter is a good GUI for iptables writen on GTK2, it has the ability to use both white and black lists for regulating traffic, it is very simple and easy to use, with good documentation available on their website.
Guarddog is a really easy to use GUI for configuring iptables. After setting up a basic desktop configuration it passes all Shields Up tests perfectly.
AUR repository.AUR requires and is available in the
To have the firewall settings applied at boot-up you must run
/etc/rc.firewall from inside
/etc/rc.local or something similar.
Uncomplicated Firewall (ufw) Frontends
Gufw, a GTK-based front-end to which happens to be a CLI front-end to iptables (gufw->ufw->iptables), is super easy and super simple to use.
kcm-ufw is a KDE alternative to Gufw.
See Uncomplicated Firewall for more info.
KMyFirewall is KDE3 GUI for iptables.
Firewall editing capabilities are simple enough to use to be suitable for beginners, but also allow for sophisticated tweaking of the firewall settings.
AUR.AUR requires and is available in the
Firewall Builder is "a GUI firewall configuration and management tool that supports iptables (netfilter), ipfilter, pf, ipfw, Cisco PIX (FWSM, ASA) and Cisco routers extended access lists. [...] The program runs on Linux, FreeBSD, OpenBSD, Windows and Mac OS X and can manage both local and remote firewalls." Source: http://www.fwbuilder.org/