Free Firewalls for Small and Medium Networks You Can Rely On!
Free Firewalls for Small and Medium Networks (Part One)
Technicians frequently receive inquiries about firewalls and which ones are best suited for use in small and medium networks. In this article, we will cover — across two parts — the most notable free firewalls that can be used. Before getting into the details of the article, I would like to note that my experience in the field of firewalls is limited, and what I will mention is based on information I have gathered from the internet. Therefore, I will provide a brief overview of each firewall and present its specifications in English from available sources.
As is well known, most available firewalls operate in a Linux, FreeBSD, or OpenBSD environment, and use various technologies such as pf (Packet Filter), ipf (IPFilter), ipfw (IPFirewall), and iptables.
Firestarter
Firestarter: An Open Source Firewall for Protecting Small Networks
Firestarter is a free, open source firewall designed to protect small computer networks. In addition to being open source, Firestarter offers many other features:
- An easy-to-use, user-friendly graphical interface
- Provides a setup wizard for configuring the firewall on first use
- Suitable for use on desktops, servers, and gateway devices
- Provides real-time monitoring of firewall events and displays intrusion attempts as they occur
- Internet connection sharing can be enabled, optionally with DHCP service for clients
- Allows defining inbound and outbound access policies
- Ability to open or block ports and configure protection with mouse clicks
- Ability to enable port forwarding to your local network in seconds
- Option to allow or block traffic
- Real-time display of firewall events
- Display of active network connections, including any traffic being routed through the firewall
- Advanced Linux kernel tuning features providing protection against flooding, broadcasting, and spoofing
- Support for configuring ICMP parameters to stop Denial of Service (DoS) attacks
- Support for configuring ToS parameters to improve services for connected client computers
- Ability to hook user-defined scripts or rule sets before or after firewall activation
- Supports Linux kernels 2.4 and 2.6
- Translation available for 38 languages (as of November 2004)
Zorp GPL
This is a new firewall for enterprises and medium-sized networks.
This new firewall was developed by several companies and is considered a next-generation firewall. This firewall is known as a "Proxy Firewall", as it operates at the Application Layer using application agents and proxies.
In addition to being a proxy firewall, this solution offers many other advantages:
- Uses the Python programming language as its configuration and decision language
- Supports multiple protocols such as HTTP/1.1, FTP, SSL, finger, plug, whois, and telnet
- Uses extensible application gateways
- Capable of analyzing sub-protocols (such as HTTP inside SSL)
- Packet filtering rules can be added/removed on demand
- Users can create their own proxy modules using Python if native versions are not available
Thanks to these advanced features, this new solution is particularly well-suited for enterprises and medium-sized networks looking for a powerful and flexible firewall.
Turtle
This is a simple and fast firewall suitable for small networks, running on a Linux environment with kernel 2.4.x. The following are the key specifications of this firewall:
- Zone, Network, Host, and Group definitions (ZONES, NETWORKS, HOSTS and GROUPS): The network can be divided into different zones or groups to control access and manage policies.
- Filter rules definitions based on services: Ability to define filtering rules and allow/deny based on the services in use.
- New services definitions: Ability to add definitions for new services not included by default.
- NAT (Network Address Translation): The ability to translate internal network addresses to external addresses.
- Masquerading: Ability to hide the identity of internal devices behind a single external address.
Thanks to these various features, this firewall is considered a simple and fast solution suitable for small networks running on a Linux environment.
LutelWall
A firewall with many distinctive and useful specifications, and the best part is that its configuration is not complicated and can be easily understood if you have a good background in networking. This firewall is built on a Linux 2.4 environment and is suitable for all types of networks. The following are its key features:
Traffic Control Features:
- Flexible traffic control capability using rule sets
- Support for user-defined protocols
- Support for multiple external and internal interfaces (and their associated aliases)
- Automatic support for MASQUERADE / SNAT
- Easy DNAT setup (transparent proxy, forwarding to LAN/DMZ)
- Bandwidth rate limiting features
- Packet marking to run external traffic shaping tools
- Traffic optimization based on Type of Service (TOS)
- Support for passive and active FTP transfers
- Support for DHCP
Security Features:
- Stateful TCP connection tracking with a restrictive TCP chain
- Blocking all types of stealth scans (FIN, Xmas Tree, Null, Windows, or ACK scan modes)
- Blocking IP protocol scans (nmap -sO)
- Blocking UDP scans (nmap -sU)
- Blocking TCP/IP fingerprint identification (nmap -O)
- Spoofing protection, including protection for aliases
- Protection against Smurf attacks
- Protection against SYN Flood attacks
- Protection against UDP / ICMP flooding
- Verification of IANA-reserved addresses
- SYSCTL parameter tuning to further increase robustness
Logging Features:
- Logging of stealth scan attempts (FIN, Xmas Tree, Null), ACK scan modes (nmap -sF -sX -sN), IP protocol scans (nmap -sO), UDP scans (nmap -sU), and nmap fingerprint identification attempts.
Other Features:
- Automatic detection of connection type (static/dynamic, external/internal)
- Automatic update of the firewall tool
- Automatic update of the IANA-reserved address list
- Display firewall statistics in native iptables format, CSV, or HTML
- Easy deployment on all distributions as well
The Floppyfw firewall program operates from a floppy disk of only 1.44 megabytes. Despite its small size, it provides a large set of security and networking features such as:
- Access lists
- IP-masquerading (Network Address Translation)
- Connection tracked packet filtering
- Advanced routing
- Traffic shaping capability
This program requires a minimum hardware specification of a 386sx processor or higher, two network cards, and at least 12 MB of RAM. If there is less than 12 MB of memory or no floating point unit, it is preferable to use version 1.0 designed for those cases as well.
Floppyfw also features a simple packaging and distribution system, and supports local and remote event logging via klogd/syslogd, as well as serial port access. It also provides DHCP services and DNS caching for internal networks.
Floppyfw is considered a suitable solution for modest hardware that provides strong network protection through a relatively small size as well.
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