- A
Brute force attack
A brute force attack systematically tries passwords or encryption keys. In this case, repeated SSH login attempts from one IP are classic signs of a password guessing attempt.
- B
Man-in-the-middle attack
Why wrong: A man-in-the-middle attack intercepts and potentially alters communication between two parties. It does not typically manifest as repeated login attempts from a single IP on a firewall log.
- C
ARP poisoning
Why wrong: ARP poisoning sends fake ARP replies to associate the attacker's MAC address with the IP of a legitimate device, enabling traffic interception. It occurs on the local network and would not appear as repeated SSH attempts from an external IP.
- D
DDoS attack
Why wrong: A Distributed Denial-of-Service (DDoS) attack floods a target with traffic from many sources to overwhelm it. A single source attempting logins does not constitute a DDoS.
Quick Answer
The correct answer is a brute force attack. This is because the firewall logs show repeated login attempts from a single external IP address targeting the SSH server, which is the hallmark of an attacker systematically trying numerous username and password combinations to gain unauthorized access. SSH, running on port 22, is a prime target for such attacks because it provides remote shell access, and automated tools like Hydra or Medusa can rapidly test credentials. On the CompTIA Network+ N10-009 exam, this scenario tests your ability to distinguish a brute force attack from a dictionary attack (which uses a curated word list) or a DoS attack (which aims to overwhelm the service). A common trap is confusing repeated attempts with a password spraying attack, but remember that spraying targets many usernames with a few common passwords, while a brute force attack hammers one account or IP with many guesses. Memory tip: think of a battering ram hitting the same door over and over—that’s brute force.
N10-009 Network Security Practice Question
This N10-009 practice question tests your understanding of network security. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. 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 auditor is reviewing firewall logs and notices repeated login attempts from a single external IP address to the company's SSH server. Which type of attack is likely occurring?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Brute force attack
Repeated login attempts from a single external IP to an SSH server are characteristic of a brute force attack, where an attacker systematically tries many username/password combinations to gain unauthorized access. SSH (port 22) is a common target because it provides remote shell access, and automated tools like Hydra or Medusa can rapidly test credentials. The firewall logs show multiple failed authentication attempts from the same source, which is the hallmark of this attack type.
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.
- ✓
Brute force attack
Why this is correct
A brute force attack systematically tries passwords or encryption keys. In this case, repeated SSH login attempts from one IP are classic signs of a password guessing attempt.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Man-in-the-middle attack
Why it's wrong here
A man-in-the-middle attack intercepts and potentially alters communication between two parties. It does not typically manifest as repeated login attempts from a single IP on a firewall log.
- ✗
ARP poisoning
Why it's wrong here
ARP poisoning sends fake ARP replies to associate the attacker's MAC address with the IP of a legitimate device, enabling traffic interception. It occurs on the local network and would not appear as repeated SSH attempts from an external IP.
- ✗
DDoS attack
Why it's wrong here
A Distributed Denial-of-Service (DDoS) attack floods a target with traffic from many sources to overwhelm it. A single source attempting logins does not constitute a DDoS.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between a brute force attack (repeated single-source login attempts) and a DDoS attack (traffic flood from multiple sources), so candidates mistakenly choose DDoS when they see 'repeated attempts' without recognizing the single-source, credential-guessing nature of the activity.
Detailed technical explanation
How to think about this question
SSH brute force attacks often target default ports and common usernames (e.g., 'root', 'admin') using wordlists like RockYou. Rate limiting, fail2ban, or SSH key-based authentication can mitigate such attacks, but firewall logs showing repeated SYN packets to port 22 with subsequent RST or timeout after failed auth attempts confirm the pattern. In real-world scenarios, attackers may rotate IPs via proxies to evade detection, but a single IP indicates a less sophisticated or early-stage attack.
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 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
Questions learners often ask
What does this N10-009 question test?
Network Security — This question tests Network Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Brute force attack — Repeated login attempts from a single external IP to an SSH server are characteristic of a brute force attack, where an attacker systematically tries many username/password combinations to gain unauthorized access. SSH (port 22) is a common target because it provides remote shell access, and automated tools like Hydra or Medusa can rapidly test credentials. The firewall logs show multiple failed authentication attempts from the same source, which is the hallmark of this attack type.
What should I do if I get this N10-009 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 2026
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