IPTraf is a console-based network statistics utility that gathers TCP connection paket and byte counts, interface statistics, and activity indicators. Also captures all TCP/UDP packets.

Protocol LAN analyzer that can monitor various interfaces: ISDN, PPP, Token Ring, standard: loopback, 10baseT Ethernet.

Allows the user to take over the IP address of another machine in the user's LAN via ARP spoofing.

A circuit-level firewall and proxy that can be used to provide convenient and secure network connectivity to a wide range of hosts. Very similar to a SOCKS implementation.

Tool that interactively builds a firewall using ipfwadm, ipchains, or netfilter/iptables firewalling. [GPL]

A log analysis program that interfaces with the SNORT open source Intrusion Detection System to provide real time visual notification when an intrusion signature has been detected on the network.

Performs emulation of other operating systems and vulnerabilities not found on the host; in order to deceive and solicit invalid attempts of exploitation by malicious individuals.

A BSD-based firewall with source included. This binaries main value is that it is perfect for beginners learning how firewalls are developed.

Performs logging of incoming IP packets by utilizing a multi-threaded approach. Administrators can perform filtering of captured packets.

A packet sniffing tool, based on the Berkeley packet capture library; that prints complete data-link, network, and transport layer header information for all packets it sees.