- A
Change the SSH port to a non-standard port number.
Why wrong: Security by obscurity is ineffective; attackers scan all ports, and this does not prevent brute-force on the new port.
- B
Disable password authentication for SSH and use key-based authentication only.
Why wrong: While more secure long-term, this does not immediately mitigate the ongoing attack and may lock out users who only have password access.
- C
Add the offending IP addresses to /etc/hosts.deny manually.
Why wrong: Manual blocking is impractical with hundreds of IPs and does not adapt to new attackers.
- D
Install and configure fail2ban to block IP addresses after 5 failed SSH attempts within 10 minutes.
fail2ban dynamically blocks offending IPs, reducing attack surface while allowing legitimate users who might mistype credentials.
LPIC-2 System Security Practice Question
This LPIC-2 practice question tests your understanding of system 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 company runs an Apache web server (port 80) and an SSH server (port 22) for remote administration. The system administrator notices that the server has become sluggish and network traffic has increased significantly. Checking /var/log/auth.log reveals hundreds of failed SSH authentication attempts per minute from diverse IP addresses targeting the 'admin' user. The administrator wants to mitigate this brute-force attack with minimal impact on legitimate users. Which course of action is most effective?
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
Install and configure fail2ban to block IP addresses after 5 failed SSH attempts within 10 minutes.
Install fail2ban to automatically block IPs after repeated failures, preventing brute-force without disrupting legitimate users who might retry.
Key principle: ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Change the SSH port to a non-standard port number.
Why it's wrong here
Security by obscurity is ineffective; attackers scan all ports, and this does not prevent brute-force on the new port.
- ✗
Disable password authentication for SSH and use key-based authentication only.
Why it's wrong here
While more secure long-term, this does not immediately mitigate the ongoing attack and may lock out users who only have password access.
- ✗
Add the offending IP addresses to /etc/hosts.deny manually.
Why it's wrong here
Manual blocking is impractical with hundreds of IPs and does not adapt to new attackers.
- ✓
Install and configure fail2ban to block IP addresses after 5 failed SSH attempts within 10 minutes.
Why this is correct
fail2ban dynamically blocks offending IPs, reducing attack surface while allowing legitimate users who might mistype credentials.
Related concept
Standard ACLs match source addresses.
Common exam traps
Common exam trap: ACLs stop at the first match
ACLs are processed top to bottom. The first matching entry wins, and an implicit deny usually exists at the end.
Detailed technical explanation
How to think about this question
ACL questions test precision: source, destination, protocol, port and direction. A generally correct ACL can still fail if it is applied on the wrong interface or in the wrong direction.
KKey Concepts to Remember
- Standard ACLs match source addresses.
- Extended ACLs can match source, destination, protocol and ports.
- The first matching ACL entry is used.
- There is usually an implicit deny at the end.
TExam Day Tips
- Check inbound versus outbound direction.
- Read the ACL from top to bottom.
- Look for a broader permit or deny above the intended line.
Key takeaway
ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
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.
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related LPIC-2 ACL questions on filtering logic and placement.
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FAQ
Questions learners often ask
What does this LPIC-2 question test?
System Security — This question tests System Security — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: Install and configure fail2ban to block IP addresses after 5 failed SSH attempts within 10 minutes. — Install fail2ban to automatically block IPs after repeated failures, preventing brute-force without disrupting legitimate users who might retry.
What should I do if I get this LPIC-2 question wrong?
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related LPIC-2 ACL questions on filtering logic and placement.
What is the key concept behind this question?
Standard ACLs match source addresses.
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Last reviewed: Jun 24, 2026
This LPIC-2 practice question is part of Courseiva's free LPI 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 LPIC-2 exam.
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