mediumMultiple SelectObjective-mapped
XK0-006 Practice Question: A Linux administrator is configuring secure…
A Linux administrator is configuring secure remote access to a server. Which three of the following are recommended best practices for securing SSH? (Choose three.)
⚠ Common exam trap
The trap here is that candidates often mistake changing the default SSH port (Option D) for a genuine security control, when it is merely obscurity and not a recommended best practice in the Linux+ exam objectives.
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
✓
Enable public key authentication.
Public key authentication (Option A) is a recommended best practice because it uses asymmetric cryptography (RSA, ECDSA, or Ed25519) to authenticate users without transmitting passwords over the network. This eliminates the risk of password interception via man-in-the-middle attacks or brute-force attempts, as the private key never leaves the client and the server verifies only the corresponding public key.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Enable public key authentication.
Why this is correct
Key-based authentication is more secure than passwords.
- ✗
Use password authentication only.
Why it's wrong here
Passwords are vulnerable to brute-force; key-based is recommended.
- ✓
Disable root login via SSH.
Why this is correct
Prevents direct root login; users must sudo.
- ✗
Change the default SSH port to a non-standard port.
Why it's wrong here
Security through obscurity; not a true best practice.
- ✓
Allow only specific users or groups.
Why this is correct
Limiting access reduces attack surface.
Quick reference
Symmetric Encryption Algorithm Comparison
| Algorithm | Key Size | Block Size | Status | Notes |
|---|---|---|---|---|
| AES-128 | 128-bit | 128-bit | Current standard | NIST approved; WPA3, TLS |
| AES-256 | 256-bit | 128-bit | Current standard | Preferred for sensitive / govt data |
| 3DES | 112-bit effective | 64-bit | Deprecated (2023) | Replaced by AES |
| DES | 56-bit | 64-bit | Broken | Cracked in < 24 h; never deploy |
| ChaCha20 | 256-bit | Stream cipher | Current | TLS 1.3, WireGuard |
Go deeper
Related to this question
Learn chapter
Linux Fundamentals and History
Key term
Risk
Risk is the possibility that an event or action will negatively affect an organization's ability to achieve its goals, often measured in terms of likelihood and impact.
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.