Advanced System Security Dr. Wayne Summers Department of Computer Science Columbus State University

2 Chapter 4: Security Policies  A security policy is a statement that partitions the states of a system into a set of authorized, or secure, states and a set of unauthorized or nonsecure, states.  A secure system is a system that starts in an authorized state and cannot enter an unauthorized state.  A breach of security occurs when a system enters an unauthorized state.  Information is confidential with respect to a set of entities if none of the entities can obtain any of the information.  Information has the property of integrity with respect to a set of entities if all of the entities trust the information.

3 Security Policies  Information has the property of availability with respect to a set of entities if all of the entities can access the information.  A security mechanism is an entity or procedures that enforces some part of the security policy.  A security model is a model that represents a particular policy or set of policies.

4 4.2 Types of Security Policies  A military security policy (governmental security policy) is a security policy developed primarily to provide confidentiality.  A commercial security policy is a security policy developed primarily to provide integrity. [transaction- oriented integrity security policy]  A confidentiality policy deals only with confidentiality.  An integrity policy deals only with integrity.

5 4.3 The Role of Trust  “When someone understands the assumptions her security policies, mechanisms, and procedures rest on, she will have a good understanding of how effective those policies, mechanisms, and procedures are.”  Example: what really happens when you install a “security” patch?

6 4.4 Types of Access Control  Discretionary access control (DAC) [identity-based access control (IBAC)] – user can set an access control mechanism to allow or deny access to an object  Mandatory access control (MAC) [rule-based access control] – system mechanism controls access to an object and an individual cannot alter that access.  An originator controlled access control (ORCON, ORGCON) bases access on the creator of an object (or the information it contains).

7 4.5 Example: Academic Computer Security Policy  General University Policy (Acceptable Use Policy (AUP)  Electronic Mail Policy –Summary –Full Policy –Implementation  See Chapter 35