Fail-Safe Defaults

5 minutes 5 Questions

Fail-safe defaults refer to the practice of designing a system to operate securely by default, ensuring that if a failure or error occurs, the system reverts to a secure state. This means that permissions and access controls are set to the most restrictive settings by default, requiring explicit authorization for any deviations. Restrictive settings prevent unauthorized access, protect sensitive data, and maintain system integrity. By designing a system with fail-safe defaults, security is implemented at the core of the system, rather than added on as an afterthought, making it more difficult for attackers to exploit vulnerabilities.

Guide to Fail-Safe Defaults

What is it?: The principle of Fail-Safe Defaults pertains to access control mechanisms in secure systems design. It primarily refers to the security measure wherein the default condition is denial of access, meaning, the system defaults to 'no access' when it is unable to determine the user's security clearance.

Importance: Implementing a model of Fail-Safe Defaults can prevent unauthorized individuals from gaining access to sensitive information by default when an error or uncertainty in security clearance arises. It limits the potential damage caused by misconfigurations or system failures.

How it works: In practice, a system implementing fail-safe defaults is set to deny all requests for access, unless permission for that specific user and specific request is granted explicitly. If the system can't validate the permission, it fails to a safe state by denying access.

Exam Tips: For exam questions on this topic, remember that you should always assume the worst-case scenario, which is system failure or inability to determine access rights. When the system fails, it must always default to a secure, 'access denied' state. Also, look for options where accessibility is clearly secured until permissions are notably confirmed. Be prepared for hypothetical situations presenting different potential system and user scenarios that test your understanding of this 'default-deny' principle.

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Question 1

A network administrator must block user access to the unused features of a router in order to follow the principle of fail-safe defaults. Which of the following practices should be implemented?

Enable all services on the router. Disable the unused services on the router. Limit user access through user accounts. Allow access to all features by default.

Correct Answer: Disable the unused services on the router.

The principle of fail-safe defaults requires that unused features or services should be disabled by default to minimize the attack surface. Disabling unused services on the router achieves this goal. The wrong answers would either not adhere to the principle, potentially increasing the risk, or not specifically address the need to block access to unused features.

Question 2

A security engineer is configuring a firewall with a fail-safe defaults policy. What should be the engineer's initial step?

Enable all firewall features and allow specific traffic. Allow all traffic by default and create rules to deny specific traffic. Create a custom rule to allow/deny traffic based on the company's security policy. Deny all traffic by default and create rules to allow specific traffic.

Correct Answer: Deny all traffic by default and create rules to allow specific traffic.

Following the principle of fail-safe defaults, a security engineer should deny all traffic by default and create rules to allow specific traffic as needed. This approach minimizes the attack surface by only allowing necessary traffic. The other answers do not adhere to the fail-safe defaults concept and could leave the network more vulnerable to attacks.

Question 3

An organization's security policy mandates the use of fail-safe defaults for all new application deployments. One team is about to deploy a new web application. Which of the following options should they choose?

Enable all features and rely on the application's built-in security mechanisms. Disable all features and enable only those necessary for the application. Allow access to all application features for authenticated users. Choose the default application configuration without any changes.

Correct Answer: Disable all features and enable only those necessary for the application.

The principle of fail-safe defaults requires disabling all unnecessary features and enabling only those required for the application's functionality. This approach minimizes the attack surface and reduces the risk of unauthorized access. The other answers either do not adhere to the principle or do not specifically address the security concerns related to fail-safe defaults.

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