The answer is that new SSH connections are blocked, but established SSH sessions remain active. This occurs because the iptables rule specifically targets new TCP connections to port 22, using the connection tracking system that distinguishes between a packet initiating a new session and a packet belonging to an already-established flow. The rule drops packets in the NEW state for SSH, while packets in the ESTABLISHED or RELATED states are permitted, preserving ongoing sessions. On the ISC2 Certified in Cybersecurity CC exam, this tests your understanding of stateful firewall behavior versus simple stateless filtering—a common trap is assuming the rule kills all SSH traffic, when in fact it only prevents fresh handshakes. The exam often presents this scenario to see if you grasp how connection tracking maintains session continuity. Memory tip: think “NEW gets the boot, ESTABLISHED stays put” to recall that only initiation is blocked.
ISC2 CC Security Principles Practice Question
This CC practice question tests your understanding of security principles. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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.
Exhibit
Refer to the exhibit.
```
Chain INPUT (policy ACCEPT)
target prot opt source destination
DROP tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:22 state NEW
```
A system administrator runs `iptables -L INPUT` and sees this rule. What is the immediate effect on the system?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
New SSH connections are blocked, but current SSH sessions remain active.
The rule drops all new TCP connections to port 22 (SSH) from any source, preventing new SSH connections.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
All SSH traffic is blocked, including established sessions.
Why it's wrong here
The rule only drops NEW state, so established connections are still allowed.
✓
New SSH connections are blocked, but current SSH sessions remain active.
Why this is correct
The rule drops NEW packets for SSH, so new connections are blocked; established connections are unaffected.
Related concept
Read the scenario before looking for a memorised answer.
✗
The rule has no effect because the policy is ACCEPT.
Why it's wrong here
The rule explicitly drops, overriding the default policy for matching traffic.
✗
All outbound SSH connections are blocked.
Why it's wrong here
This is the INPUT chain, so it affects incoming traffic, not outbound.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CC question in full detail.
Identify which CC exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Security Principles — This question tests Security Principles — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: New SSH connections are blocked, but current SSH sessions remain active. — The rule drops all new TCP connections to port 22 (SSH) from any source, preventing new SSH connections.
What should I do if I get this CC question wrong?
Identify which CC exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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