The Top Ten Free Network Security Tools

Network security can seem like a complex and expensive undertaking. With so many commercial offerings, and so many expensive ones, it can appear that spending more makes things more secure. This may not be the case. There are free, open source tools available to help you secure your network. Here are the top ten.

Nagios provides network monitoring as well as problem notification and management. Nagios has enterprise-class features, has been around for over 10 years, and has a large user base & support community. Nagios runs on Linux or Unix based operating systems. You can monitor Windows systems and other devices with it as well.

Regular traceroute and ICMP tools to map networks may be foiled by firewalls. But you can still see what may be on the other side of a firewall using Hping. Use this tool to see what your firewall reveals about the systems and networks it's protecting.

Ntop is a tool for network traffic monitoring including protocol information & statistics. Information can be sorted or detailed by host, subnet, or viewed in total for the network. Ntop works with NetFlow and sFlow as well. It can be compiled for Windows as well as Unix.

Netfilter is the Linux firewall software that replaces and improves upon the older ipchains firewall. Netfilter provides stateless and stateful packet filtering, for IPV4 and IPV6, NAT and port translation and much more. You may recognize iptables as the interface for it. If you need a custom firewall, proxy, or NAT solution this is the open source solution.

Wireshark is my tool for sniffing and capturing network traffic, as well as examining protocols and sessions in depth. Whether you need to capture wireless ethernet traffic, or examine specific session content, this is an indispensable tool. Wireshark runs on many platforms, and supports many capture file formats.