SPAM

http://www.monkeys.com/spam-defined/

http://www.spamhaus.org

FIREWALLS

http://www.howstuffworks.com/firewall.htm

http://www.zonelabs.com/store/content/home.jsp

VIRUSES

http://www.norton.com/

http://www.networkassociates.com/us/index.asp

http://www.webopedia.com/TERM/v/virus.html

SPYWARE

http://www.webopedia.com/TERM/s/spyware.html