NSE4 Firewall Policies and NAT Practice Question
Which statement best describes the implicit deny policy at the end of a FortiGate policy list?
⚠ Common exam trap
A common mix-up: candidates think the implicit deny can be configured or removed like an explicit policy, but FortiGate enforces it as an unchangeable, always-present rule that cannot be logged or repositioned.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
It is always present and denies any traffic that does not match an explicit allow policy
The implicit deny policy is a built-in, last-resort rule at the bottom of the FortiGate policy list that silently drops any traffic not matching an explicit allow policy. It cannot be moved, disabled, or deleted because it is a fundamental security mechanism ensuring that only explicitly permitted traffic is allowed through the firewall.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
It denies all traffic that does not match any explicit policy, and it logs the denied traffic
Why it's wrong here
The implicit deny does block any traffic that fails to match an explicit policy, but it does not log that traffic. Logging is a configurable feature that applies only to explicit firewall policies; the implicit deny rule has no log setting and silently drops unmatched packets. To capture logs for denied traffic, an administrator must create an explicit deny policy with logging enabled at the end of the policy list.
- ✗
It can be moved to a different position in the policy list
Why it's wrong here
The implicit deny policy is a fixed, non-movable entry that always resides at the bottom of the FortiGate policy list, enforcing a default traffic block for any packet not matched by an explicit allow rule. It is tempting to think this policy can be repositioned because administrators routinely reorder explicit policies to control evaluation priority. However, the implicit deny is not a configurable object; it is a hard-coded final rule, so it cannot be dragged to another position.
- ✗
It can be disabled or deleted by the admin
Why it's wrong here
The implicit deny is a built-in, non-removable security rule that cannot be disabled or deleted by an administrator. It is not a configurable object in the policy list, but rather a hard-coded final entry that always remains in effect. Since FortiGate enforces a fail-closed posture, there is no administrative toggle or deletion command that can remove this default deny behavior.
- ✓
It is always present and denies any traffic that does not match an explicit allow policy
Why this is correct
The implicit deny is always present as the last effective rule in the FortiGate policy list, regardless of how many explicit policies are configured. Any traffic that does not match an explicit allow policy is dropped by this default rule, ensuring that all unmatched packets are blocked. This is a mandatory security control that cannot be removed or repositioned, providing a safe default deny posture.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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