Fundamentals of IT systems security architecture :
1) Compartmentalization – IT system resources of different sensitivity should be located in different security zones (also known as Segmentation).
2) Defense in Depth – Protection of IT system resources is based on many security layers which complement and ensure one another (known also as
Layered Protections).
3) Adequate Protection – Protections should be relevant to the threats and values of the resources being protected (i.e., risk analysis results), compliant
with law and other regulations, and properly cooperative with other IT system elements.
4) Least Privilege – Subjects should have minimal privileges to IT resources which are necessary to perform company’s business task.
5) Secure Weakest Link in the Chain – Security level of IT system depends on the least secured element of the system.
More Security Rules:
1) Choke Point – Access to IT system resources in the network should be provided through controlled, limited number of communication channels.
2) Defense in Multiple Places – Security elements are distributed in different places of IT system. Defense through Diversification – Safety of IT system resources should be based on the protection layers consisting of different kinds of safeguards (also known as Diversity of Defense).
3) Simplicity – The design and safeguards configuration should be simple and clear, and if technically possible, based on widely approved standards. Due Diligence – Ensuring IT system safety requires continual activities that test that the protection mechanisms are operational and that security incidents are being detected and resolved.
4) Information Hiding – The IT system makes available only the information that is necessary for the company’s business operations (also known as Security through Obscurity). In the designs of intrusion prevention systems the principle is known as Attack Surface Reduction.
Need To Know – IT system users and administrators should have access to the information relevant to their position and performed duties.
5) Single Point of Failure – Protection against failures is achieved by using redundant elements, so called High-Availability (HA). Fail-Safe Stance – Access to IT system resources should be denied automatically in case of the safeguards failure (important for data-sensitive assets).
Fail-Open Stance – Network communication is passed through without control in case of the safeguards failure (important for mission-critical assets)