The answer is that the email traffic is not subject to SSL inspection, so URLs in encrypted emails are not filtered. This is correct because web filtering operates at the application layer, inspecting HTTP and HTTPS URLs; however, when phishing links bypass web filter in encrypted email, the FortiGate cannot decrypt the encrypted SMTP or IMAP/POP3 traffic to extract those URLs from the email body. Without SSL inspection, the web filter profile remains blind to the links inside encrypted messages, regardless of the 'Phishing' category being blocked. On the Fortinet NSE 4 Network Security Professional NSE4 exam, this scenario tests your understanding of how deep packet inspection and SSL/TLS decryption are prerequisites for effective web filtering on email traffic. A common trap is assuming the web filter alone can catch all phishing links, but it cannot see into encrypted payloads. Remember the memory tip: "No decrypt, no detect" — if the traffic is encrypted, the filter is effectively blind.
NSE4 Security Profiles Practice Question
This NSE4 practice question tests your understanding of security profiles. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
An administrator configures a web filter profile to block the 'Phishing' category. Users still report receiving phishing emails with links that bypass the filter. What is the most likely reason?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The email traffic is not subject to SSL inspection, so URLs in encrypted emails are not filtered.
Option B is correct because web filtering operates at the application layer and inspects HTTP/HTTPS URLs. If SSL inspection is not enabled, the FortiGate cannot decrypt the encrypted SMTP or IMAP/POP3 traffic to extract URLs from the body of emails. Without decryption, the web filter profile cannot see the phishing links inside encrypted email messages, so they bypass the filter regardless of the category being blocked.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 users are accessing the phishing sites via IP address, not URL.
Why it's wrong here
Phishing emails typically contain URLs, not IP addresses.
✓
The email traffic is not subject to SSL inspection, so URLs in encrypted emails are not filtered.
Why this is correct
Without SSL inspection, the FortiGate cannot see the URLs in the encrypted email.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The web filter profile is not applied to the firewall policy governing email traffic.
Why it's wrong here
The administrator said they configured the profile, so it should be applied.
✗
The FortiGate's URL database is outdated.
Why it's wrong here
An outdated database might miss new phishing sites, but the category block should still work for known sites.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume web filtering applies to all traffic equally, forgetting that encrypted email traffic requires SSL inspection to extract URLs from the message body, whereas web filtering for HTTP traffic works without decryption.
Detailed technical explanation
How to think about this question
Under the hood, FortiGate's web filter uses a proxy-based or flow-based engine to inspect HTTP/HTTPS requests. For email traffic, the URLs are often embedded in the body of SMTP, IMAP, or POP3 sessions. Without SSL/TLS inspection (via a deep inspection profile), the FortiGate cannot decrypt the TLS-encrypted email session to extract the URLs. Even if the web filter profile is correctly applied, the encrypted payload is opaque, so the phishing links remain invisible to the filter. In real-world scenarios, administrators must enable SSL inspection for email protocols (e.g., SMTP, IMAPS, POP3S) and apply a web filter profile to the firewall policy handling that traffic.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the NSE4 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Security Profiles — This question tests Security Profiles — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The email traffic is not subject to SSL inspection, so URLs in encrypted emails are not filtered. — Option B is correct because web filtering operates at the application layer and inspects HTTP/HTTPS URLs. If SSL inspection is not enabled, the FortiGate cannot decrypt the encrypted SMTP or IMAP/POP3 traffic to extract URLs from the body of emails. Without decryption, the web filter profile cannot see the phishing links inside encrypted email messages, so they bypass the filter regardless of the category being blocked.
What should I do if I get this NSE4 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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