Glaswegian

Defence in Depth is arguably the most time tested principle in security and applies to physical security as well as online. It builds on a concept of a hardened "core" where one places their "crown jewels." This core is then surrounded by castle walls and moats, with ever increasing generality of defence.

It's a great concept, but comes at a price. Just as the area covered is wider from layer to layer, so is the cost associated with protecting against more plentiful, and less and less specific threats. A firewall typically acts as the last line of defense on the enterprise perimeter, but has to protect against a great many varieties of threats, while a server room door has to "only" be concerned with physical access.

Another flaw in the Defence in Depth design is its inherent difficulty to implement vis-à-vis the three basic tenets of security: confidentiality, integrity and availability. Why? Because most forms of defence create increasing confidentiality, but make integrity more difficult to implement and manage. Any increase in defence, of course, makes availability that much harder to provide to the users.

A difficulty that I myself encountered many times is the applicability of Defence in Depth to my "layer 8" problem, the users. If users are not trained properly, if they are not aware of information protection needs, methods, and the "why?" of it, they become a liability, rather than an asset, towards data security. If you are like me, you find the need to increase our moat to user ratio on an ongoing base harder to design, implement, manage, and pay for. Many of us just say "this is reality" and define our demarcation line as a physical device, such as a router, an access point, a firewall or a webserver. There are potentially two things wrong with doing so:

1. We are basically saying "we are a target just waiting to be attacked"

2. We allow most barbarians (in the form of rogue traffic, networks and devices) to hit our gates


http://features.techworld.com/securi...depth/?olo=rss