There are a variety of Usenet newsgroups that you might find an interesting source of information on network security and related topics:
comp.security.announce - computer security announcements, including new CERT-CC advisories
comp.security.unix - UNIX security
comp.security.misc - miscellaneous computer and network security
comp.security.firewalls - proposed newsgroup on firewalls; might never be created
alt.security - alternative discussions of computer and network security
comp.admin.policy - computer administrative policy issues, including security
comp.protocols.tcp-ip - TCP/IP internals, including security
comp.unix.admin - UNIX system administration, including security
comp.unix.wizards - UNIX kernel internals, including security