CERT Coordination Center Tech Tips with info such as how to recover from an incident, Intruder Detection Checklist, etc. NIST Security Publications with lots of papers. Commonly used by hackers. Mosts systems need to replace or patch older sendmail versions. Also read their information about secure DNS that makes sure all DNS entries are correctly signed.
Socks is a proxy protocol for firewall traversal and remote access to servers.
A good security resource. Security information from Univ.