Quick Answer
The answer is the FortiGuard Antivirus Service. This subscription is required because it provides the signature updates that the FortiGate firewall downloads to keep its antivirus database current; without an active subscription, the device cannot retrieve new definitions, leaving the network vulnerable to emerging threats. On the Fortinet NSE 4 Network Security Professional exam, this concept tests your understanding of how FortiGuard subscription services map to specific security functions—a common trap is confusing the FortiGuard Antivirus Service with the FortiGuard Web Filtering or IPS services, which handle different update streams. Remember that antivirus signatures are exclusively tied to the AV subscription, not to any unified threat management bundle. A helpful memory tip: think “AV for AV”—Antivirus Service for Antivirus signatures.
This NSE4 practice question tests your understanding of high availability and diagnostics. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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A FortiGate administrator receives an alert that the FortiGuard antivirus database on the firewall is outdated. Which subscription service must be active to update the antivirus signatures?
FortiGuard IPS Service
Why wrong: IPS updates protect against intrusion attempts, not antivirus signatures.
FortiGuard Application Control Service
Why wrong: Application control updates are different.
FortiGuard Antivirus Service
This service provides antivirus signature updates.
FortiGuard Web Filtering Service
Why wrong: URL filtering updates are separate.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
FortiGuard Antivirus Service
Option B is correct. The FortiGuard Antivirus Service (AV) provides signature updates for antivirus scanning. Without a valid subscription, updates fail.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
FortiGuard IPS Service
Why it's wrong here
IPS updates protect against intrusion attempts, not antivirus signatures.
FortiGuard Application Control Service
Why it's wrong here
Application control updates are different.
FortiGuard Antivirus Service
Why this is correct
This service provides antivirus signature updates.
Related concept
Static NAT maps one inside address to one outside address.
FortiGuard Web Filtering Service
Why it's wrong here
URL filtering updates are separate.
Common exam traps
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related NSE4 NAT questions on configuration and troubleshooting.
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FAQ
High Availability and Diagnostics — This question tests High Availability and Diagnostics — Static NAT maps one inside address to one outside address..
The correct answer is: FortiGuard Antivirus Service — Option B is correct. The FortiGuard Antivirus Service (AV) provides signature updates for antivirus scanning. Without a valid subscription, updates fail.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related NSE4 NAT questions on configuration and troubleshooting.
Static NAT maps one inside address to one outside address.
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Last reviewed: Jun 21, 2026
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.
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