Quick Answer
The answer is UDP flood detection, port scan detection, and TCP port sweep detection. These three types of IPS anomaly detection are correct because FortiGate’s IPS engine identifies anomalous network behavior by comparing traffic patterns against established baselines; UDP flood detection flags an abnormal volume of UDP packets, port scan detection spots reconnaissance via multiple connection attempts to different ports from a single source, and TCP port sweep detection catches sequential connection attempts to the same port across multiple destinations. On the Fortinet NSE 4 exam, this question tests your understanding of how anomaly detection differs from signature-based detection—a common trap is confusing TCP port sweep with port scan, but remember that port scan targets multiple ports on one host, while a sweep targets one port across many hosts. A helpful memory tip is to think of “flood, scan, sweep” as the three anomalous behaviors that deviate from normal traffic baselines.
This NSE4 practice question tests your understanding of security profiles. 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 FortiGate is configured with an IPS profile to detect and block anomalous network behavior. Which THREE types of detection does IPS anomaly detection include? (Choose three.)
Protocol decoding
Why wrong: Protocol decoding is a separate IPS method for detecting protocol violations, not anomaly detection.
Port scan detection
Port scanning is a common anomaly that IPS can detect.
SYN flood detection
SYN flood is a rate-based anomaly that IPS can detect.
Signature-based detection
Why wrong: Signature-based is distinct from anomaly detection.
UDP flood detection
UDP flood is another rate-based anomaly.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Port scan detection
Port scan detection is a type of anomaly detection in FortiGate's IPS profile that identifies reconnaissance attempts by monitoring for multiple connection attempts to different ports from a single source. This behavior deviates from normal traffic patterns and is flagged as anomalous, allowing the IPS to block potential scanning activity before an attack progresses.
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.
Protocol decoding
Why it's wrong here
Protocol decoding is a separate IPS method for detecting protocol violations, not anomaly detection.
Port scan detection
Why this is correct
Port scanning is a common anomaly that IPS can detect.
Related concept
Read the scenario before looking for a memorised answer.
SYN flood detection
Why this is correct
SYN flood is a rate-based anomaly that IPS can detect.
Related concept
Read the scenario before looking for a memorised answer.
Signature-based detection
Why it's wrong here
Signature-based is distinct from anomaly detection.
UDP flood detection
Why this is correct
UDP flood is another rate-based anomaly.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
The trap here is that candidates often confuse signature-based detection (Option D) with anomaly detection, but FortiGate explicitly separates these into distinct IPS detection methods, and the question asks specifically for anomaly detection types.
Detailed technical explanation
FortiGate's IPS anomaly detection uses a baseline learning period to establish normal traffic thresholds for metrics such as packets per second or connections per second. When traffic exceeds these thresholds (e.g., more than 1000 SYN packets per second from a single IP), the IPS triggers an anomaly event. This is distinct from signature-based detection, which matches patterns like 'HTTP GET /etc/passwd' against a database of known exploits.
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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Security Profiles — study guide chapter
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FAQ
Security Profiles — This question tests Security Profiles — Read the scenario before looking for a memorised answer..
The correct answer is: Port scan detection — Port scan detection is a type of anomaly detection in FortiGate's IPS profile that identifies reconnaissance attempts by monitoring for multiple connection attempts to different ports from a single source. This behavior deviates from normal traffic patterns and is flagged as anomalous, allowing the IPS to block potential scanning activity before an attack progresses.
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 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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