Difficulty: Medium
Correct Answer: Designing systems so that when a failure or uncertainty occurs, the default behavior is to deny access or move to a safe state rather than granting access or operating in an unsafe way
Explanation:
Introduction / Context:
The fail safe approach, often described as fail safe defaults, is a cornerstone of secure system design. It deals with how systems behave when something goes wrong or when there is insufficient information to make a perfect decision. Instead of prioritizing convenience, a fail safe design prioritizes safety and security, even if that sometimes means denying legitimate access temporarily. This question asks you to identify the definition that captures this idea.
Given Data / Assumptions:
Concept / Approach:
A fail safe system is designed so that failure leads to a state that minimizes harm or exposure. In security, this usually means defaulting to deny rather than allow. For example, if an access control list cannot be loaded, the system should deny access until the policy is known rather than assume everyone is allowed. If a firewall rule set is incomplete, it should block traffic that does not match known safe rules. This principle contrasts with fail open behavior, where failure leads to relaxed controls. Fail safe defaults protect confidential data and system integrity by treating ambiguous situations as potential threats rather than as automatic approvals.
Step-by-Step Solution:
Step 1: Identify that fail safe relates to how systems respond under failure or uncertainty.
Step 2: Recognize that in security, safety means denying access or limiting operations when correct checks cannot be performed.
Step 3: Recall examples such as locked doors by default, strict firewall rules when configuration fails, or login systems that refuse authentication if the user database is unavailable.
Step 4: Select the option that explicitly states that failure leads to denial of access or a safe state rather than unsafe openness.
Verification / Alternative check:
Security best practices and classic design principles emphasize that systems should not grant access unless it is explicitly permitted by policy and successfully validated. Case studies of breaches often involve fail open behavior, where systems permitted actions after a partial failure. Training materials use examples like elevators stopping rather than dropping when a failure occurs as an analogy for fail safe design. These references align with the statement in option A and clearly reject behaviors that grant unrestricted access on error.
Why Other Options Are Wrong:
Option B is the opposite of fail safe because granting full access on failure creates a dangerous fail open condition. Option C is wrong because disabling all security by default exposes users and contradicts the idea of secure defaults. Option D misinterprets fail safe; backups need to occur before failures to preserve data, not after corruption. Option E is incomplete and misleading; physical locks might be part of a strategy, but ignoring logical controls in software undermines overall security and does not address failure behavior.
Common Pitfalls:
Organizations sometimes choose convenience over safety, implementing designs that fail open to reduce support calls when a component goes down. This can lead to serious security incidents if attackers trigger failures deliberately to bypass checks. Another pitfall is assuming that rare failures do not need careful handling. Proper fail safe design requires thinking through unusual conditions and ensuring that the system defaults to a conservative, secure posture. By adopting the fail safe approach described in option A, you reduce the chance that unexpected errors will become easy paths for attack or data loss.
Final Answer:
Designing systems so that when a failure or uncertainty occurs, the default behavior is to deny access or move to a safe state rather than granting access or operating in an unsafe way
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