Cisco CyberOps Associate (CBROPS) 200-201Security ConceptsHard
A security analyst is reviewing a firewall's configuration rules. One rule permits all outbound traffic from the internal network to the internet, while another rule explicitly denies traffic to known malicious IP addresses. However, if a rule for a specific type of traffic (e.g., a particular port) is not explicitly defined, the firewall automatically blocks it. Which firewall rule philosophy is being applied here?
- APermit Any Any
- BImplicit Deny
- CExplicit Allow
- DLeast Privilege
Show answer & explanationAnswer & explanation
Correct answer: B. Implicit Deny
Implicit Deny is a fundamental firewall philosophy where any traffic not explicitly permitted by a rule is automatically denied. The scenario states that 'if a rule for a specific type of traffic is not explicitly defined, the firewall automatically blocks it,' which is the definition of implicit deny.
Why the other options are wrong
- A. Permit Any Any is the opposite, allowing all traffic by default.
- C. Explicit Allow means specific traffic is allowed, but doesn't define the default action for unmentioned traffic.
- D. Least Privilege applies to user/process access, not directly to network firewall rules.
Implicit Deny
A fundamental security principle and firewall rule philosophy where any access or traffic that is not explicitly permitted by a rule is automatically denied. This ensures a secure default posture, limiting potential attack surfaces.
- Default action is to deny access.
- Requires explicit permission for all allowed traffic.
- Enhances security by limiting exposure.
- Opposite of 'Permit Any Any'.
Memory trick: Implicit Deny is like a club where you're not allowed in unless your name is on the list.