Quick Answer
The answer is `PasswordAuthentication no` in the `/etc/ssh/sshd_config` file. This directive is correct because it explicitly disables the ability to log in using a password, forcing the SSH daemon to rely solely on key-based authentication, which eliminates the risk of brute-force password attacks. On the CompTIA Linux+ XK0-005 exam, this question tests your understanding of SSH server hardening and the specific syntax required in the configuration file—a common trap is confusing `PasswordAuthentication` with `PubkeyAuthentication` or forgetting that the setting must be changed from the default `yes` to `no`. Remember that after editing the file, you must restart the `sshd` service for the change to take effect. A useful memory tip: think of "Password No" as your security lockdown—if you want to block password logins, set `PasswordAuthentication` to `no`.
This XK0-005 practice question tests your understanding of security. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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.
After a security audit, it is recommended to disable SSH password authentication in favor of key-based authentication. Which configuration line should be set in /etc/ssh/sshd_config?
PasswordAuthentication yes
Why wrong: Enables password authentication, against policy.
PubkeyAuthentication no
Why wrong: Disables public key authentication, opposite of desired.
PasswordAuthentication no
Disables password authentication, correct.
ChallengeResponseAuthentication yes
Why wrong: May still allow password-based methods.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
PasswordAuthentication no
Option C is correct because disabling password authentication forces SSH to use key-based authentication, which is more secure against brute-force attacks. Setting `PasswordAuthentication no` in `/etc/ssh/sshd_config` prevents SSH from prompting for a password, requiring a valid SSH key pair for authentication. This aligns with the security audit's recommendation to disable password authentication in favor of key-based authentication.
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.
PasswordAuthentication yes
Why it's wrong here
Enables password authentication, against policy.
PubkeyAuthentication no
Why it's wrong here
Disables public key authentication, opposite of desired.
PasswordAuthentication no
Why this is correct
Disables password authentication, correct.
Related concept
Read the scenario before looking for a memorised answer.
ChallengeResponseAuthentication yes
Why it's wrong here
May still allow password-based methods.
Common exam traps
The trap here is that candidates often confuse `PasswordAuthentication` with `PubkeyAuthentication` or think that disabling password authentication requires setting it to `yes`, when in fact the directive must be set to `no` to disable it.
Detailed technical explanation
Under the hood, SSH key-based authentication uses asymmetric cryptography: the client proves possession of the private key, and the server verifies against the public key stored in `~/.ssh/authorized_keys`. Disabling `PasswordAuthentication` also prevents fallback to keyboard-interactive password prompts, but note that `ChallengeResponseAuthentication` and `KbdInteractiveAuthentication` (in newer OpenSSH versions) can still allow password authentication via PAM if not also disabled. In real-world scenarios, a common mistake is to only set `PasswordAuthentication no` without also disabling `ChallengeResponseAuthentication` or `UsePAM`, which can leave a password-based path open.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A practitioner preparing for the XK0-005 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
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
Security — This question tests Security — Read the scenario before looking for a memorised answer..
The correct answer is: PasswordAuthentication no — Option C is correct because disabling password authentication forces SSH to use key-based authentication, which is more secure against brute-force attacks. Setting `PasswordAuthentication no` in `/etc/ssh/sshd_config` prevents SSH from prompting for a password, requiring a valid SSH key pair for authentication. This aligns with the security audit's recommendation to disable password authentication in favor of key-based authentication.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 25, 2026
This XK0-005 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 XK0-005 exam.
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