[1] Wikipedia - IP address spoofing: https://en.wikipedia.org/wiki/IP_address_spoofing

[2] ZoneAlarm: http://www.zonelabs.com/

[3] Snort - the Lightweight Network Intrusion Detection System: http://www.snort.org/

[4] Hardening Security Tips for Linux Servers: https://www.tecmint.com/linux-server-hardening-security-tips/

[5] Sunsolve: The Solaris Fingerprint Database: www.oracle.com/technetwork/articles/systems-hardware-architecture/solaris-fingerprint-db-277032.pdf

[6] SANS Institute: Information Security Reading Room: What is an Egress Filter and How Can I Implement it? www.sans.org/reading_room/whitepapers/firewalls/egress-filtering-faq_1059

[7] The Nessus Project: http://www.nessus.org/products/nessus/. A current list of backdoors recognised by Nessus can be found at: http://www.nessus.org/plugins/index.php?view=all&family=Backdoors.