Various tools for network penetration testing. Please do not abuse them.

arpspoof     redirect packets from a target host (or all hosts) on the LAN
             intended for another host on the LAN by forging ARP replies.
dnsspoof     forge replies to arbitrary DNS address / pointer queries on
             the LAN.
dsniff       simple password sniffer.
filesnarf    saves selected files sniffed from NFS traffic in the current
             working directory.
macof        flood the local network with random MAC addresses.
mailsnarf    a fast and easy way to violate the Electronic Communications
             Privacy Act of 1986 (18 USC 2701-2711), be careful.
msgsnarf     record selected messages from sniffed AOL Instant Messenger,
             ICQ 2000, IRC, and Yahoo! Messenger chat sessions.
sshmitm      SSH monkey-in-the-middle.
tcpkill      kills specified in-progress TCP connections.
tcpnice      slow down specified TCP connections via "active" traffic
             shaping.
urlsnarf     output all requested URLs sniffed from HTTP traffic in CLF
             (Common Log Format, used by almost all web servers), suitable
             for offline post-processing
webmitm      HTTP / HTTPS monkey-in-the-middle.
webspy       sends URLs sniffed from a client to your local Netscape
             browser for display, a fun party trick

WWW: http://www.monkey.org/~dugsong/dsniff/