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Thu, Oct 1, 2009 10:11 EDT

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Posted by: Ariel Silverstone in Best Practices Topic: MobileBlog: Bare Knuckles Security
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בע"ה Evolution of Defense in Depth
As security professionals will tell you, one of the basic principles of a good security program is the concept of Defense in Depth. Defense in Depth is arguably the most time-tested principle in Security, and applies to physical security, as well as information security. Defense in Depth builds on a concept of a hardened “core”, where one places their “crown jewels”. This core is then surrounded by castle walls and motes, with ever increasing generality of defense.
Defense in Depth is a great concept, but it comes at a price. Just as the area covered is wider from layer to layer, so is the cost associated with protecting with against more plentiful and less and less specific threats. A firewall, for example, that typically acts as the last line of defense on the enterprise perimeter, has to protect against a great many varieties of threats, while a server-room door has to “only” be concerned with physical access.

The Server Room in The Center of The Castle
Another flaw in the Defense 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 defense create increasing Confidentiality, but make Integrity more difficult to implement and manage. Any increase in defense, of course, makes the concept of Availability that much harder to provide to the users.
A difficulty that I myself encountered many times is the applicability of Defense 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 resign ourselves to the proverbial “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:
If we continue to do so, we will have approached a mathematical certainty of being hacked, or at least DDoS’ed out of the Net. I really prefer NOT to draw analogies here to the real world, and we all know which those are.
Not only is the problem above big enough to cause some to lose sleep, but imagine what happens when we move to a Cloud topology… there we have nothing but moats and walls and front doors. These front doors can be any browser, on any device, anywhere in the world. How do you protect yourself against that? Speaking of losing sleep - I love coffee, but this is ridiculous.

Clouds, Doors, and Windows. Source: desktopnexus.com (Heavily edited)
Like any solution that might involve our entire user set, which may include Internet users, rather than pure corporate users, any solution must be: