Secure Systems Architecture and Trusted Computing Bases
Architecture Under Adversarial Pressure
Security Architecture
Secure architecture starts by minimizing the trusted computing base, reducing privilege, and separating concerns so that compromise of one component does not imply compromise of the whole system. This requires deliberate design of interfaces, isolation, and recovery paths.
Core Architectural Concepts
Monolith vs Microsegmented Design
Monolithic Design
- Simpler to deploy
- Bigger blast radius if compromised
Microsegmented Design
- More complex to operate
- Limits lateral movement and containment scope
What is the most direct purpose of compartmentalization?
Compartmentalization limits how far an attacker can move after compromising one part of the system.
Correct answer: Reduce the blast radius of compromise
Define the trusted computing base in one sentence.
Understanding the TCB is essential for evaluating where assurance effort should be concentrated.
Correct answer: The trusted computing base is the set of hardware, software, and processes that must remain correct for the system’s security goals to hold.
Designing for Resilience
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Step 1: Identify critical assets and dependencies.
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Step 2: Minimize privileges and reachable interfaces.
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Step 3: Separate high-risk functions into isolated components.
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Step 4: Build secure defaults and fail-safe behavior.
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Step 5: Plan detection, rollback, and recovery mechanisms.
Which design principle most directly limits the permissions granted to a service?
Least privilege ensures services have only the access they need to perform their functions.
Correct answer: Least privilege
Architectural Insight
Security architecture is often about controlling failure modes, not preventing every failure.