With the number and variety of internet attacks increasing month by month, firewalls have become an essential security requirement for any public-facing network. The free Linux operating system offers a unique set of firewall tools, second-to-none in sophistication and reliability, making it an ideal choice for building a firewall machine. With iptables now standardised within the 2.4 kernel release, Linux has become a truly state-of-the-art security system, offering finely-grained packet-filtering at both the TCP/IP and ICMP layers.

Our knowledge and experience of configuring iptables can help you protect your network with the best tools available and at zero software cost. Since dedicated Linux firewall machines require only low processor power, memory and disk space the associated hardware costs are also minimal for small office networks.

Our thorough approach to the technicalities of configuring firewalls covers:

• Establishing iptables rules
• Setting-up Network Address Translation (NAT)
• Disabling services not essential to the network
• Configuring TCP/IP addressing
• Packet-filtering at the TCP/IP and ICMP levels
• Protection against attack via unprivileged ports
• Filtering ICMP Control and Status messages
• Logging dropped packets
• Denying access from problematic sites
• Debugging firewall rules
• Setting-up system logs
• Authentication and authorisation within the filesystem
• Configuring Secure Shell (SSH)
• Tripwire installation and configuration
• Installing and configuring intrusion detection software