XK0-006 Security Practice Question
A system administrator is hardening SSH and needs to disable root login and password authentication. Which two directives should be set in /etc/ssh/sshd_config?
⚠ Common exam trap
A common mix-up: candidates confuse ChallengeResponseAuthentication with PasswordAuthentication, or assume DenyUsers is a valid directive for blocking root, when the correct syntax is PermitRootLogin no.
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
✓
PermitRootLogin no and PasswordAuthentication no
Disabling root login and password authentication are two separate directives in sshd_config. PermitRootLogin no prevents direct SSH access for the root user, and PasswordAuthentication no disables password-based logins, forcing the use of key-based authentication. Both directives are required to meet the hardening goal.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
PermitRootLogin no and ChallengeResponseAuthentication no
Why it's wrong here
PermitRootLogin no correctly disables root login, but ChallengeResponseAuthentication governs keyboard-interactive authentication, not password authentication, so password logins remain enabled. It is tempting because both are genuine sshd_config directives, and ChallengeResponseAuthentication would be correct when disabling keyboard-interactive prompts such as OTP challenges.
- ✗
DenyUsers root and PasswordAuthentication no
Why it's wrong here
DenyUsers root blocks the root account at authentication but leaves PermitRootLogin at its default, and PasswordAuthentication no does disable password logins. It is tempting because DenyUsers is a valid sshd_config access-control directive, and would be correct when restricting specific named accounts rather than the root login method.
- ✓
PermitRootLogin no and PasswordAuthentication no
Why this is correct
PermitRootLogin no blocks direct root SSH sessions, forcing administrators to authenticate as unprivileged users before escalating via sudo. PasswordAuthentication no disables password-based logins entirely, requiring key-based authentication instead. Together these directives satisfy both hardening constraints in the stem, eliminating brute-force and credential-guessing attack vectors against the SSH daemon.
- ✗
PermitRootLogin prohibit-password and PasswordAuthentication yes
Why it's wrong here
PermitRootLogin prohibit-password still allows root to authenticate by key, and PasswordAuthentication yes explicitly enables the password logins the hardening requires disabling. It is tempting because prohibit-password is a legitimate restrictive value, and would be correct when root must retain key-based access while password logins are blocked.
Go deeper
Related to this question
Learn chapter
User and Group Administration
Key term
User
A user is any person, system, or device that interacts with an IT service, resource, or identity system, typically authenticated through credentials and authorized to perform specific actions.
Key term
SSH
SSH (Secure Shell) is a cryptographic network protocol that provides secure, encrypted communication and remote administration between two devices over an unsecured network.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This XK0-006 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 XK0-006 exam.