Quick Answer
The answer is a port scan. In Security Onion, when an analyst uses Squert and observes a high volume of alerts from a single source IP hitting many different destination ports, this pattern directly matches the behavior of a port scan, where an attacker systematically probes ports to find open services. Each probe, such as a SYN packet to a unique port, triggers a separate IDS alert, creating the spike in alerts. On the Cisco CyberOps Associate 200-201 exam, this scenario tests your ability to distinguish reconnaissance activity from actual exploitation; a common trap is confusing this with a DDoS or brute-force attack, but the key differentiator is the single source targeting varied ports rather than a single service. For a memory tip, think of a "single shooter, many doors" — one IP knocking on every port door, which is the hallmark of a port scan.
This 200-201 practice question tests your understanding of network intrusion analysis. 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.
In Security Onion, an analyst runs 'squert' and sees a high number of alerts from a single source IP across multiple destination ports. What is the most likely cause?
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.
Denial of service
Why wrong: DoS attacks flood a single target, not multiple ports.
SQL injection
Why wrong: SQL injection targets web applications, not multiple ports.
Port scan
A port scanner probes multiple ports to discover services.
Phishing attack
Why wrong: Phishing involves social engineering, not network scanning.
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
Squert is a web interface for Sguil in Security Onion that visualizes alert data from the intrusion detection system (IDS). A high number of alerts from a single source IP targeting multiple destination ports is a classic signature of a port scan, where the attacker probes a range of ports on one or more targets to discover open services. The IDS triggers multiple alerts because each probe (e.g., SYN packets to different ports) matches a detection rule, such as those for TCP SYN scans.
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.
Denial of service
Why it's wrong here
DoS attacks flood a single target, not multiple ports.
SQL injection
Why it's wrong here
SQL injection targets web applications, not multiple ports.
Port scan
Why this is correct
A port scanner probes multiple ports to discover services.
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.
Phishing attack
Why it's wrong here
Phishing involves social engineering, not network scanning.
Common exam traps
Cisco often tests the distinction between a port scan and a denial of service attack, where candidates mistakenly associate 'high number of alerts' with DoS, but the key differentiator is the single source IP targeting multiple destination ports versus overwhelming a single service.
Detailed technical explanation
Under the hood, a port scan like a TCP SYN scan sends packets with the SYN flag set to various ports; the IDS (e.g., Snort or Suricata) uses rules such as 'alert tcp $EXTERNAL_NET any -> $HOME_NET 1:1024' to detect this, and squert aggregates these alerts by source IP. In a real-world scenario, an attacker might use a tool like Nmap with a 'sS' scan, generating thousands of alerts in seconds, which an analyst can pivot on in squert to identify the scanning host. A subtle behavior is that some IDS rules may threshold alerts to avoid flooding the console, but squert still shows the aggregated count.
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
Network Intrusion Analysis — This question tests Network Intrusion Analysis — Read the scenario before looking for a memorised answer..
The correct answer is: Port scan — Squert is a web interface for Sguil in Security Onion that visualizes alert data from the intrusion detection system (IDS). A high number of alerts from a single source IP targeting multiple destination ports is a classic signature of a port scan, where the attacker probes a range of ports on one or more targets to discover open services. The IDS triggers multiple alerts because each probe (e.g., SYN packets to different ports) matches a detection rule, such as those for TCP SYN scans.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 25, 2026
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