CompTIA Tech+ (FC0-U71)SecurityMedium
A network administrator is configuring a new firewall to restrict outbound internet access for employees to only necessary business applications. The administrator configures rules to allow traffic on specific ports for HTTP, HTTPS, and DNS, while blocking all other ports by default. This approach is an example of which security principle?
- ADefense in depth
- BImplicit deny
- CSeparation of duties
- DLeast privilege
Show answer & explanationAnswer & explanation
Correct answer: B. Implicit deny
Implicit deny is a security principle where if a rule explicitly permits access, it is allowed; otherwise, it is denied by default. By configuring the firewall to block all other ports by default, the administrator is implementing implicit deny.
Why the other options are wrong
- A. Defense in depth involves using multiple layers of security controls.
- C. Separation of duties divides critical tasks among multiple individuals to prevent fraud or error.
- D. Least privilege grants users or systems only the minimum necessary permissions to perform their tasks.
Implicit Deny
A security principle, commonly applied in firewalls and access control lists, stating that if a specific action (e.g., network traffic, access to a resource) is not explicitly permitted, it is automatically denied.
- Default security posture is to deny.
- Only explicitly allowed actions are permitted.
- Enhances security by reducing attack surface.
Memory trick: Implicit Deny: If it's not on the 'allow' list, it's denied.