Port Scanners
http://www.insecure.org/nmap
http://www.apostols.org/projectz/queso/
Ping Sweep Tools
http://www.stanford.edu/~schemers/docs/fping/fping.html
http://www.technotronic.com/rhino9/software/pinger.htm
Port scan and ping sweep detection tools
http://www.openwall.com/scanlogd/
http://www.kalug.lug.net/tcplogd/
http://pltplp.net/ippl/
http://ojnk.sourceforge.net/
http://www.psionic.com/abacus/portsentry/ pingd is featured in route's article in Phrack magazine as listed below
Hacking Exposed: Network Security Secrets and Solutions, Stuart McClure, Joel Scambray, and George Kurtz, McGraw-Hill, 1999.
Network Intrusion Detection: An Analyst's Handbook, Stephen Northcutt, New Riders Publishing, 1999.
“Linux Ping Daemon”, by Fyodor, Phrack Magazine, Volume 8, Issue 52, January 26, 1998, Article 7. http://phrack.infonexus.com/search.phtml?view&article=p52-7
“The Art of Port Scanning”, by route@infonexus.com, Phrack Magazine, Volume 7, Issue 51, September 1, 1997, Article 11. http://phrack.infonexus.com/search.phtml?view&article=p51-11
“Remote OS detection via TCP/IP Stack Fingerprinting”, by Fyodor, Phrack Magazine, Volume 8, Issue 54, December 25, 1998, Article 9. http://phrack.infonexus.com/search.phtml?view&article=p54-9
Lance Spitzner's whitepapers and publications: http://www.enteract.com/~lspitz/pubs.html
BUGTRAQ Mailing List: http://www.securityfocus.com