CompTIA Tech+ (FC0-U71)SecurityMedium
A network administrator is configuring a new firewall for a company. The company policy states that all network traffic not explicitly allowed should be blocked by default. Which firewall rule concept is being applied here?
- ADemilitarized Zone (DMZ)
- BStateful Inspection
- CPort Forwarding
- DImplicit Deny
Show answer & explanationAnswer & explanation
Correct answer: D. Implicit Deny
The 'Implicit Deny' principle states that if a firewall rule does not explicitly allow traffic, that traffic is automatically denied. This ensures that only authorized communication can pass through, making it a fundamental security best practice.
Why the other options are wrong
- A. A DMZ is a network segment for public-facing servers, not a rule concept for blocking unallowed traffic.
- B. Stateful inspection tracks connection states but doesn't define the default action for unallowed traffic.
- C. Port forwarding redirects traffic from one port to another, not a general blocking principle.
Implicit Deny
A security principle in firewalls and access control lists (ACLs) that states any traffic or access not explicitly permitted is automatically denied.
- Fundamental security best practice.
- Ensures only necessary traffic is allowed.
- Often the last rule in a firewall's rule set.
Memory trick: If it's not explicitly OPEN, it's IMPLICITLY DENIED.