XK0-006 Security Practice Question
An administrator is configuring a firewall using iptables to block all incoming traffic except SSH on port 22. Which three rules correctly implement this? (Choose THREE.)
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
✓
iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
The correct approach: set default policy to DROP on INPUT, then allow established/related connections, then allow SSH. The other options either drop all (blocking SSH), use wrong chain, or allow all.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
iptables -A INPUT -p tcp --dport 22 -j DROP
Why it's wrong here
Drops SSH, opposite of goal.
- ✓
iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
Why this is correct
Allows established and related connections.
- ✓
iptables -A INPUT -p tcp --dport 22 -j ACCEPT
Why this is correct
Allows SSH traffic on port 22.
- ✗
iptables -A INPUT -j DROP
Why it's wrong here
Drops all input; would block SSH unless rule is placed after SSH rule, but order matters.
- ✓
iptables -P INPUT DROP
Why this is correct
Sets default policy to DROP for incoming traffic.
Go deeper
Related to this question
Learn chapter
Firewall and Security Basics
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.
Key term
Policy
A policy is a set of rules or guidelines that defines how an organization manages, secures, and operates its IT systems and services.
About these practice questions
One of 979 original XK0-006 practice questions on Courseiva, each with a full explanation and wrong-answer analysis — not exam dumps or protected exam content. Learn why practice questions differ from exam dumps →
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.