Security Boundaries
A security boundary is the line of separation between two areas, subnets, or environments with differing security requirements. One of the most common examples is the boundary between a local area network (LAN) and the internet. Recognizing security boundaries is crucial, whether they exist in a network or the physical world. Once a boundary is identified, it is essential to implement mechanisms to control the flow of information across it.
Types of Security Boundaries
Security boundaries can take many forms depending on the classification and functions of the objects and subjects within an environment. For instance, classification boundaries may exist between objects with different security levels, defining which subjects can interact with them.
Moreover, security boundaries exist between the physical and logical environments:
- Logical Security Boundaries refer to where electronic communications interface with devices or services under the organization’s legal responsibility.
- Physical Security Boundaries refer to perimeters in the physical world, such as office walls, building perimeters, or fences, that limit access to protected areas.
Both types of boundaries are necessary for a comprehensive security framework, and they must be addressed separately in security policies.
Defining and Implementing Security Boundaries
Clear definition of security boundaries is crucial to ensure that unauthorized access is prevented. In a logical environment, boundaries are often marked by devices or services for which the organization is responsible, and unauthorized subjects are warned against accessing these areas.
In the physical environment, security perimeters are reflected by structures like walls or fences. Warning signs often indicate that unauthorized access is prohibited and that breaches will result in prosecution.
When transforming security policies into actual controls, consider each environment separately. The goal is to deploy reasonable, cost-effective solutions that protect the value of the objects within the boundary. Over-investing in countermeasures beyond the value of the objects being protected can be wasteful.
