The informational links listed here should help you to better evaluate the security of a network and to become familiar with the tools that will be used against them. These materials are presented as a starting point, and they will provide links to other resources for further exploration.

CIAC - U.S. Department of Energy's Computer Incident Advisory Capability
CERT - Computer Emergency Response Team Coordination Center
CSI - Computer Security Institute
CSRC - NIST Computer Security Resource Clearinghouse

Info Security News - Info Security News Service
Security News Portal - Security News Portal
SANS News Bites - Weekly Security Highlights

WWW Security FAQ - WWW server and browser security how-tos
Interactive Security Policies and Reference Center - Security policy references
Infosyssec - Security Portal
Neohapsis - Security mailing list archive