Quick Answer
The answer is to change the SSH port to a high-numbered port and restrict source IPs. This is correct because SSH brute force mitigation relies on reducing the service’s discoverability and attack surface; moving SSH from the default port 22 evades automated scanners that target only standard ports, while restricting source IPs limits which hosts can even initiate a connection, effectively blocking the external IP’s repeated attempts. On the CISSP exam, this scenario tests your understanding of defense in depth and access control—specifically how obscurity (port change) combined with explicit authorization (IP restriction) can provide immediate risk reduction without disabling the service entirely. A common trap is assuming a firewall rule change alone is sufficient, but the key is making the service less visible to automated brute-force tools. Memory tip: “Hide the door, then lock the guest list”—port change hides the door, IP restriction locks the guest list.
This CISSP practice question tests your understanding of communication and network security. 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 security analyst is reviewing network logs and sees repeated failed connection attempts from an external IP to the company's SSH server (port 22). The firewall has a rule allowing SSH from anywhere. What is the best immediate action to reduce risk?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Remove the firewall rule allowing SSH.
Why wrong: That would block all SSH, not just malicious.
Disable SSH access entirely.
Why wrong: SSH is needed for administration.
Change the SSH port to a high-numbered port and restrict source IPs if possible.
Changing the port reduces automated scans, and restricting source IPs adds defense.
Block the offending IP address in the firewall.
Why wrong: The attacker can easily use a different IP.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Change the SSH port to a high-numbered port and restrict source IPs if possible.
Option C is correct because changing the SSH port to a non-standard, high-numbered port reduces automated scanning and brute-force attacks by evading default port 22 scans, while restricting source IPs adds a layer of access control. This balances security with operational continuity, as SSH remains available for legitimate administrative use. The immediate risk reduction comes from making the service less discoverable and limiting the attack surface without fully disabling remote access.
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.
Remove the firewall rule allowing SSH.
Why it's wrong here
That would block all SSH, not just malicious.
Disable SSH access entirely.
Why it's wrong here
SSH is needed for administration.
Change the SSH port to a high-numbered port and restrict source IPs if possible.
Why this is correct
Changing the port reduces automated scans, and restricting source IPs adds defense.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Block the offending IP address in the firewall.
Why it's wrong here
The attacker can easily use a different IP.
Common exam traps
The trap here is that candidates often choose Option D (block the offending IP) because it seems like a quick fix, but they fail to recognize that automated attacks rotate IPs constantly, making this a temporary and ineffective solution compared to changing the port and restricting sources.
Detailed technical explanation
SSH daemons (e.g., OpenSSH) listen on port 22 by default, making them prime targets for automated bots using tools like Shodan or masscan. Changing to a high port (e.g., 2222) reduces the noise from random scans, but does not stop targeted attacks; combining this with source IP whitelisting (via firewall ACLs or hosts.allow) creates defense-in-depth. In real-world scenarios, organizations often pair port obfuscation with fail2ban or rate-limiting to dynamically block repeated failures, but the immediate action should be to reduce exposure while maintaining service availability.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A security team runs a vulnerability scan on a web application and discovers an unpatched SQL injection flaw. The team prioritises remediation by CVSS score — critical flaws are patched within 24 hours, high within 7 days. Questions like this test whether you understand vulnerability management processes, scanning tools, and remediation prioritisation.
What to study next
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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FAQ
Communication and Network Security — This question tests Communication and Network Security — Read the scenario before looking for a memorised answer..
The correct answer is: Change the SSH port to a high-numbered port and restrict source IPs if possible. — Option C is correct because changing the SSH port to a non-standard, high-numbered port reduces automated scanning and brute-force attacks by evading default port 22 scans, while restricting source IPs adds a layer of access control. This balances security with operational continuity, as SSH remains available for legitimate administrative use. The immediate risk reduction comes from making the service less discoverable and limiting the attack surface without fully disabling remote access.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 2026
This CISSP practice question is part of Courseiva's free ISC2 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 CISSP exam.
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