Quick Answer
The correct answer is that the ACCEPT rule matches before the DROP rule. This is because iptables processes rules in strict sequential order, and the first matching rule in a chain determines the packet’s fate; in this scenario, the ACCEPT rule for SSH (typically matching port 22) appears earlier in the chain, so incoming SSH packets are permitted immediately and never reach the subsequent DROP rule. On the Systems Security Certified Practitioner SSCP exam, this tests your understanding of firewall rule ordering and common misconfigurations—a frequent trap is assuming a general deny at the end of a chain will block traffic, when a preceding allow rule has already accepted it. Remember the memory tip: "First match wins, so place your denies before your allows for broad blocks, or your allows before your denies for specific exceptions."
This SSCP practice question tests your understanding of security operations and administration. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
Refer to the exhibit. A security analyst reviews these iptables rules and expects SSH access to be blocked, but it is still allowed. What is the MOST likely reason?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
The DROP rule does not apply to SSH.
Why wrong: The rule specifically targets port 22 (SSH).
The DROP rule is misconfigured with wrong source.
Why wrong: Source is 0.0.0.0/0, which matches all.
The ACCEPT rule matches before the DROP rule.
iptables processes rules in order; the first match wins.
The default policy allows traffic, overriding the DROP rule.
Why wrong: Default policy only applies if no rule matches.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
The ACCEPT rule matches before the DROP rule.
C is correct because iptables processes rules in sequential order, and the first matching rule determines the packet's fate. In this scenario, the ACCEPT rule for SSH (typically matching on port 22) appears before the DROP rule in the chain, so incoming SSH packets match the ACCEPT rule first and are permitted, never reaching the subsequent DROP rule. This is a classic ordering issue where a more specific allow rule precedes a general deny rule.
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.
The DROP rule does not apply to SSH.
Why it's wrong here
The rule specifically targets port 22 (SSH).
The DROP rule is misconfigured with wrong source.
Why it's wrong here
Source is 0.0.0.0/0, which matches all.
The ACCEPT rule matches before the DROP rule.
Why this is correct
iptables processes rules in order; the first match wins.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
The default policy allows traffic, overriding the DROP rule.
Why it's wrong here
Default policy only applies if no rule matches.
Common exam traps
The trap here is that candidates often assume iptables evaluates all rules and applies the most restrictive one, but in reality, iptables uses first-match logic, so rule order is critical.
Detailed technical explanation
iptables chains are traversed in order, and each rule is a conditional statement; once a match occurs, the target (e.g., ACCEPT, DROP) is executed and traversal stops for that packet. This is defined by the netfilter framework in the Linux kernel, where rules are stored as a linked list. In real-world scenarios, misordered rules are a common cause of firewall policy violations, and tools like `iptables -L -n -v` can show packet counters to identify which rules are being hit.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A security analyst at a medium-sized enterprise encounters this scenario during an investigation or architecture review. The correct answer reflects best practice for the specific threat or control described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Security exam questions test whether you can match controls to threats in context — not just recall definitions.
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 Operations and Administration — This question tests Security Operations and Administration — Read the scenario before looking for a memorised answer..
The correct answer is: The ACCEPT rule matches before the DROP rule. — C is correct because iptables processes rules in sequential order, and the first matching rule determines the packet's fate. In this scenario, the ACCEPT rule for SSH (typically matching on port 22) appears before the DROP rule in the chain, so incoming SSH packets match the ACCEPT rule first and are permitted, never reaching the subsequent DROP rule. This is a classic ordering issue where a more specific allow rule precedes a general deny rule.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 25, 2026
This SSCP practice question is part of Courseiva's free ISC2 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 SSCP exam.
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