Note: Links are valid as of March 2016.
Cyber crime: www.justice.gov/criminal-ccips/
Computer security: www.cert.org
Symantec’s antivirus site: www.symantec.com/security_response/
FBI Cyber Crime: www.fbi.gov/about-us/investigate/cyber
Hellbound Hackers: www.hellboundhackers.org/
Dark Reading: www.darkreading.com/
NMap: www.nmap.org
SecTools: http://sectools.org/tag/port-scanners/
Ophcrack: http://ophcrack.org/
Password crackers: http://resources.infosecinstitute.com/10-popular-password-cracking-tools/
Various security and hacking tools: insecure.org
Snort, an open source IDS system: www.snort.org/
The SANS Institute IDS FAQ: www.sans.org/resources/idfaq/
The Association of Computing Machinery IDS page: http://xrds.acm.org/
WhoIs tool: http://whois.domaintools.com/
Various search tools: www.virtualgumshoe.com/
Viewing previous versions of websites: www.Archive.org
www.all-internet-security.com/security_scanners.html
Scanning tool: www.rawlogic.com/netbrute/
CNET Virus Center: www.cnet.com/topics/security/
F-Secure: www.fsecure.com
Symantec virus encyclopedia: www.symantec.com/security_response/
vxHeaven: vxheaven.org/