This NSE7 practice question tests your understanding of advanced threat protection. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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.
A security administrator wants to block email spoofing attacks against their organization's domain. They configure SPF, DKIM, and DMARC records. Which protocol authenticates the domain of the email sender by verifying the email's signature against a public key published in DNS?
SPF
Why wrong: SPF checks the sending IP address against authorized servers.
ARC
Why wrong: ARC preserves email authentication results across intermediaries, not primary authentication.
DKIM
DKIM signs emails with a private key; the public key in DNS verifies the signature.
DMARC
Why wrong: DMARC uses SPF and DKIM results to determine policy.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
DKIM
DKIM (DomainKeys Identified Mail) is the correct answer because it provides email authentication by allowing the sender to cryptographically sign an email with a private key. The receiving mail server then retrieves the sender's public key from a DNS TXT record and verifies the signature, confirming that the email was not tampered with and originates from a domain the sender is authorized to use.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
SPF
Why it's wrong here
SPF checks the sending IP address against authorized servers.
ARC
Why it's wrong here
ARC preserves email authentication results across intermediaries, not primary authentication.
DKIM
Why this is correct
DKIM signs emails with a private key; the public key in DNS verifies the signature.
Related concept
Read the scenario before looking for a memorised answer.
DMARC
Why it's wrong here
DMARC uses SPF and DKIM results to determine policy.
Common exam traps
The trap here is that candidates often confuse SPF's IP-based verification with DKIM's cryptographic signature verification, or they assume DMARC performs the actual authentication, when in fact DMARC only enforces policies based on SPF and DKIM results.
Detailed technical explanation
Under the hood, DKIM uses asymmetric cryptography: the signing domain publishes a public key in a DNS TXT record (e.g., 'default._domainkey.example.com'), and the sender's MTA generates a hash of selected email headers and body, encrypting it with the private key to create the 'DKIM-Signature' header. A subtle but critical behavior is that DKIM verification can pass even if the email is forwarded, as long as the signature covers the original headers and body, which is why ARC was later developed to handle forwarding scenarios. In a real-world attack, a threat actor could spoof the 'From' address of a legitimate domain; without DKIM, the receiver has no cryptographic proof of origin, making DKIM essential for detecting such spoofing.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
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FAQ
Advanced Threat Protection — This question tests Advanced Threat Protection — Read the scenario before looking for a memorised answer..
The correct answer is: DKIM — DKIM (DomainKeys Identified Mail) is the correct answer because it provides email authentication by allowing the sender to cryptographically sign an email with a private key. The receiving mail server then retrieves the sender's public key from a DNS TXT record and verifies the signature, confirming that the email was not tampered with and originates from a domain the sender is authorized to use.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
This NSE7 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 NSE7 exam.
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