Security: Defense in Depth

Defense in Depth isn't just a military tactic anymore. This is another basic building block of IT security. In short, don't rely on one specific type of security for your valuable data and expect attacks to come from every vector possible.

Defense in depth starts with securing your systems physically. Anything that's really sensitive should be behind locked doors. Firewalls, separate sensitive networks, OS-level security, anti-virus, anti-malware, intrusion detection systems, and many other tactics can help ensure that what needs to be secure actually is.

Typically you'll want to combine multiple levels of security for additional assurance.