A secure data center design must start with the assumption that no piece of software or hardware can be trusted to be 100 percent secure. But, if that assumption is true, how do we design a secure system?
A good general security principle is “defense in depth."? Avoid relying on a single protection method and deploy security in layers designed so that a hacker has to defeat multiple defense mechanisms before completing a successful attack.
For example, packet filtering that blocks access from network addresses outside the organization keeps attackers out even if they have stolen access passwords. Data encryption can protect information confidentiality even when someone breaks physical security and taps into communication wires.
Different versions of the same defense in a mechanism can also be layered. For example, an attacker can neutralize a firewall by exploiting a known design flaw. Deploying two firewalls in series using distinct technologies makes it more difficult for someone to penetrate the network.
User authentication may require not only a user name and password, but also the presentation of a token card and/or a biometric pattern (such as a fingerprint scan). Stealing a password may be easy, but obtaining it and a physical device at the same time is far more difficult.
A defense mechanism that is layered on top of another does not necessarily have to be unbreakable. Sometimes, all that is required is to delay the attack and buy enough time so that the intrusion can be detected and diverted by other means.