If you read the Top 10 Network Security Tools (Part 1). Here is the continuation.

6. Hping2 - A network probing utility like ping on steroids. This handy little utility assembles and sends custom ICMP, UDP, or TCP packets and then displays any replies. It was inspired by the ping command, but offers far more control over the probes sent.

7. Kismet - A powerful wireless sniffer. Kismet is an console (ncurses) based 802.11 layer2 wireless network detector, sniffer, and intrusion detection system. It identifies networks by passively sniffing (as opposed to more active tools such as NetStumbler), and can even decloak hidden (non-beaconing) networks if they are in use. It can automatically detect network IP blocks by sniffing TCP, UDP, ARP, and DHCP packets, log traffic in Wireshark/TCPDump compatible format, and even plot detected networks and estimated ranges on downloaded maps. As you might expect, this tool is commonly used for wardriving.

8. TCPDump - The classic sniffer for network monitoring and data acquisition. Tcpdump is the IP sniffer we all used before Ethereal (Wireshark) came on the scene, and many of us continue to use it frequently. It may not have the bells and whistles (such as a pretty GUI or parsing logic for hundreds of application protocols) that Wireshark has, but it does the job well and with fewer security holes.

9. Cain and Abel - The top password recovery tool for Windows. UNIX users often smugly assert that the best free security tools support their platform first, and Windows ports are often an afterthought. They are usually right, but Cain & Abel is a glaring exception.

10. John the Ripper - A powerful, flexible, and fast multi-platform password hash cracker. John the Ripper is a fast password cracker, currently available for many flavors of Unix (11 are officially supported, not counting different architectures), DOS, Win32, BeOS, and OpenVMS. Its primary purpose is to detect weak Unix passwords. It supports several crypt(3) password hash types which are most commonly found on various Unix flavors, as well as Kerberos AFS and Windows NT/2000/XP LM hashes.