Textbooks:

1.  Northcutt, Stephen and Judy Novak. Network Intrusion Detection. Indianapolis: New Riders, 2002.
2. The Tao of Network Security Monitoring: Beyond Intrusion Detection- Richard Bejtlich (Addison-Wesley Professional)

Webliography:

IANA port numbers

http://www.iana.org/assignments/port-numbers

NMAP Security Scanner for network exploration and Security Audits

http://www.nmap.org

Network port scanning and Computing system policy

http://www.ecu.edu/cs-itcs/policies/scanning.cfm