XK0-006 Security Practice Question
A Linux administrator wants to prevent users from reusing their last five passwords. Which PAM module should be configured?
⚠ Common exam trap
A common mix-up: candidates confuse pam_pwquality (which enforces password strength) with pam_pwhistory (which enforces password reuse prevention), leading them to select pam_pwquality when the question specifically asks about preventing reuse of previous passwords.
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
✓
pam_pwhistory
The pam_pwhistory module is specifically designed to enforce password history policies by storing a user's previous passwords in a separate file (e.g., /etc/security/opasswd) and preventing reuse of those passwords. By configuring the 'remember' option in the PAM stack, the administrator can set the number of previous passwords that cannot be reused, such as 'remember=5' to block the last five passwords.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
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pam_faillock
Why it's wrong here
pam_faillock locks accounts after repeated failed authentication attempts, addressing brute-force lockout rather than password history. Preventing reuse of the last five passwords requires pam_pwhistory, which stores previous hashes and rejects matches. pam_faillock is correct when the requirement is temporary account lockout after failed logins.
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pam_pwquality
Why it's wrong here
pam_pwquality enforces complexity rules such as length, character classes, and dictionary checks at password change time. It does not retain previous password hashes, so it cannot detect reuse. pam_pwquality is correct when the requirement is enforcing minimum length or mixed-character composition, not history.
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pam_unix
Why it's wrong here
pam_unix performs standard password verification against the shadow file and handles account ageing, but it keeps no history of prior hashes. Preventing reuse of the last five passwords requires pam_pwhistory with remember=5. pam_unix is correct when the requirement is basic authentication or password expiry management.
- ✓
pam_pwhistory
Why this is correct
Configuring pam_pwhistory with the remember=5 parameter stores previous password hashes and rejects any new password matching them, directly enforcing the five-password reuse restriction in the stem. It hooks into the password stack, so changes are blocked at the point of update rather than merely advised.
Go deeper
Related to this question
Learn chapter
User and Group Administration
Key term
PAM
Privileged Access Management (PAM) is a security framework that controls, monitors, and audits access to critical systems and accounts with elevated permissions.
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.
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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.