NSE4 Security Profiles Practice Question
A FortiGate administrator receives reports that users cannot access a legitimate website that uses HTTPS. The web filtering profile is configured with strict FortiGuard categories and 'monitor all' for unknown sites. The firewall policy has an SSL/SSH inspection profile set to 'deep-inspection'. What is the most likely cause of the issue?
⚠ Common exam trap
Many exam-takers confuse a certificate validation failure (caused by self-signed or untrusted certificates) with a web filtering category block, but the presence of deep inspection and 'monitor all' for unknown sites points directly to the SSL inspection process, not the web filter.
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
✓
The website uses a self-signed certificate which is not trusted by the FortiGate CA bundle
The most likely cause is that the website uses a self-signed certificate, which is not included in the FortiGate's trusted CA bundle. When deep inspection is enabled, the FortiGate acts as a man-in-the-middle and must validate the server's certificate against its CA store; a self-signed certificate fails this validation, causing the connection to be blocked. This is a common issue with strict inspection profiles that require trusted certificates.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
The website uses a self-signed certificate which is not trusted by the FortiGate CA bundle
Why this is correct
Deep inspection requires the FortiGate to trust the server certificate. A self-signed or untrusted CA certificate will cause the connection to fail.
- ✗
The antivirus profile is blocking a file on the website
Why it's wrong here
Antivirus blocking occurs after decryption; the issue is during the SSL handshake.
- ✗
The DNS filter is blocking the domain
Why it's wrong here
DNS filter would block at DNS query time, not cause an SSL error.
- ✗
The website's FortiGuard category is set to 'block'
Why it's wrong here
If the category were blocked, the traffic would be blocked before SSL handshake, not cause a certificate error.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This NSE4 practice question is part of Courseiva's free Fortinet certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the NSE4 exam.