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.
Which TWO of the following are recommended best practices for securing a Linux server that is publicly accessible?
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 the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use a firewall to restrict access to only necessary ports.
Options A and D are correct. Disabling root login via SSH and using a firewall to allow only necessary ports are standard security practices. Option B is incorrect because running services as root increases risk. Option C is incorrect because NFS is generally not recommended over the internet. Option E is incorrect because passwords should be complex, not simple.
Key principle: Authentication proves identity; authorization controls what that identity can do after login. Both must work for full privileged access.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Run all services with root privileges.
Why it's wrong here
Running services as root creates a large attack surface.
✗
Set all user passwords to simple, memorable ones.
Why it's wrong here
Weak passwords are easily guessed or cracked.
✓
Use a firewall to restrict access to only necessary ports.
Why this is correct
Reduces the attack surface by limiting exposed services.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Authentication checks who the user is.
✗
Enable NFS exports for file sharing.
Why it's wrong here
NFS is not secure over the internet without additional encryption.
✓
Disable direct root login via SSH.
Why this is correct
Prevents brute-force attacks on the root account.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Authentication checks who the user is.
Common exam traps
Common exam trap: authentication is not authorization
Logging in proves the user can authenticate. It does not automatically mean the user is allowed to enter privileged or configuration mode. Watch for AAA authorization, privilege level and command authorization details.
Detailed technical explanation
How to think about this question
This kind of question is testing the difference between identity and permission. A user may successfully log in to a router because authentication is working, but still fail to enter configuration mode because authorization is missing, misconfigured or mapped to a lower privilege level.
KKey Concepts to Remember
Authentication checks who the user is.
Authorization controls what the user is allowed to do after login.
Privilege levels affect access to EXEC and configuration commands.
AAA, TACACS+ and RADIUS can separate login success from command access.
TExam Day Tips
→Do not assume successful login means full administrative access.
→Look for words such as cannot enter configuration mode, privilege level, authorization or command access.
→Separate login problems from permission problems before choosing the answer.
Key takeaway
Authentication proves identity; authorization controls what that identity can do after login. Both must work for full privileged access.
Real-world example
How this comes up in practice
A junior network technician can log in to a core router but cannot reach the enable prompt or configuration mode. The AAA server is authenticating the login — but the authorisation policy only grants privilege level 1, not 15. Authentication (who you are) is working; authorisation (what you can do) is not.
What to study next
Got this wrong? Here's your next step.
Review Cisco AAA concepts — authentication, authorization, and accounting. Study privilege levels (0–15), command authorization under TACACS+, and how RADIUS differs. Then practise related LPIC-2 questions on access control and AAA configuration.
System Security — This question tests System Security — Authentication checks who the user is..
What is the correct answer to this question?
The correct answer is: Use a firewall to restrict access to only necessary ports. — Options A and D are correct. Disabling root login via SSH and using a firewall to allow only necessary ports are standard security practices. Option B is incorrect because running services as root increases risk. Option C is incorrect because NFS is generally not recommended over the internet. Option E is incorrect because passwords should be complex, not simple.
What should I do if I get this LPIC-2 question wrong?
Review Cisco AAA concepts — authentication, authorization, and accounting. Study privilege levels (0–15), command authorization under TACACS+, and how RADIUS differs. Then practise related LPIC-2 questions on access control and AAA configuration.
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?
Authentication checks who the user is.
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