Google's web security course

http://code.google.com/p/browsersec/wiki/Main
http://code.google.com/edu/security/index.html

DNS security flaws

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In practice the DNS service behaves very much like the /etc/hosts file on your computer, which is where the system initially looks up name resolutions before relying on the DNS system. The file is basically a list of IP addresses followed by the name you've associated with those IP addresses. For example, if you edit the file you can associate any domain name with any IP address of your choosing.

1. Open Terminal and enter the following command to edit the hosts file

sudo pico /etc/hosts

2. Go to the bottom of the file and enter the following:

74.125.19.106 www.apple.com

3. Press control-o followed by the return key to save the file

security issues with safari

http://support.apple.com/kb/HT3949