http://www.ethereal.com/
http://www. freshmeat .net/
http://www. insecure .org/nmap/index.html
http://www.nessus.org/
http://www.openssh.com/
http://www.openwall.com/john/ (John the Ripper)
http://www. rpmfind .net/
http://www.snort.org/
http://www. sourceforge .net/
http://www.tcpdump.org/
http://www.tripwire.com/