- A
Disable password authentication and use SSH keys only
Why wrong: While good practice, it doesn't address the overly permissive source IP.
- B
Change the SSH port to a non-standard port
Why wrong: Hiding the port is not a robust security control; it can be discovered by scanning.
- C
Add a deny rule for SSH in the network ACL
Why wrong: A deny rule in NACL would block all SSH, making the server inaccessible.
- D
Restrict the source IP address to the company's public IP range
This limits SSH access to trusted IPs only.
Question 726 of 997
CV0-004 Security Practice Question
This CV0-004 practice question tests your understanding of 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 cloud administrator notices that a security group rule allowing SSH (port 22) from any IP address (0.0.0.0/0) was created for a Linux server. The server is used for administrative purposes only. Which security best practice should be applied to reduce the attack surface?
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.
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
✓
Restrict the source IP address to the company's public IP range
Restricting the source IP address to the company's public IP range (option D) directly reduces the attack surface by limiting SSH access to only trusted administrative networks. This is the most effective security best practice because it prevents unauthorized external hosts from even attempting to connect to port 22, regardless of authentication method or port obscurity. In cloud environments like AWS, security group rules are stateful and evaluated before any packet reaches the instance, making source IP restriction a fundamental layer of defense.
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.
- ✗
Disable password authentication and use SSH keys only
Why it's wrong here
While good practice, it doesn't address the overly permissive source IP.
- ✗
Change the SSH port to a non-standard port
Why it's wrong here
Hiding the port is not a robust security control; it can be discovered by scanning.
- ✗
Add a deny rule for SSH in the network ACL
Why it's wrong here
A deny rule in NACL would block all SSH, making the server inaccessible.
- ✓
Restrict the source IP address to the company's public IP range
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse authentication hardening (option A) or port obfuscation (option B) with network-layer access control, failing to recognize that the most fundamental security best practice is to limit the source IP range to trusted administrative networks.
Detailed technical explanation
How to think about this question
Security groups in AWS act as a virtual firewall at the instance level, and rules are evaluated in a 'deny by default' model where only explicitly allowed traffic is permitted. By restricting the source CIDR to the company's public IP range, you eliminate the possibility of SYN flood attacks or SSH brute-force attempts from arbitrary IPs, as packets from outside the range are dropped before reaching the instance's network interface. In a real-world scenario, even with strong SSH key authentication, leaving port 22 open to 0.0.0.0/0 exposes the server to automated scanning tools like Shodan and can lead to resource exhaustion from connection attempts.
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 security administrator must allow nursing staff to reach a patient records server while blocking access from the guest Wi-Fi VLAN. After applying an extended ACL, traffic is still blocked from nursing workstations. The ACL was applied outbound instead of inbound on the wrong interface. Questions like this test ACL direction and placement rules.
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this CV0-004 question test?
Security — This question tests Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Restrict the source IP address to the company's public IP range — Restricting the source IP address to the company's public IP range (option D) directly reduces the attack surface by limiting SSH access to only trusted administrative networks. This is the most effective security best practice because it prevents unauthorized external hosts from even attempting to connect to port 22, regardless of authentication method or port obscurity. In cloud environments like AWS, security group rules are stateful and evaluated before any packet reaches the instance, making source IP restriction a fundamental layer of defense.
What should I do if I get this CV0-004 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
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.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jul 4, 2026
This CV0-004 practice question is part of Courseiva's free CompTIA 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 CV0-004 exam.
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