The answer is an atomic signature. This is correct because an atomic signature is defined as a single, fixed pattern that triggers an alert based on content match within a single packet, with no need for stateful inspection or correlation across multiple packets. The string '/etc/passwd' is a literal, static pattern—exactly what an atomic signature looks for—so the IDS fires immediately upon seeing that content in the payload. On the Cisco CyberOps Associate 200-201 exam, this question tests your ability to distinguish atomic signatures from composite or stateful signatures, which require tracking sequences or context across packets. A common trap is confusing atomic with composite signatures, but remember: atomic = one packet, one pattern, no state. For a quick memory tip, think of the word "atom" as the smallest indivisible unit—just like an atomic signature fires on a single, indivisible content match without needing any surrounding context.
200-201 Network Intrusion Analysis Practice Question
This 200-201 practice question tests your understanding of network intrusion analysis. 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.
A security analyst analyzes an IDS alert that triggered on the string '/etc/passwd'. What type of signature is this?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Atomic signature
The string '/etc/passwd' is a single, fixed pattern that the IDS matches against a single packet payload. This is the definition of an atomic signature: it looks for a specific content string without requiring any state or context from previous packets. Option C is correct because the alert is triggered solely by the presence of that literal string in a packet, not by any sequence of events or statistical deviation.
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.
✗
Stateful signature
Why it's wrong here
Incorrect. Stateful signatures track connection state, not just a static pattern.
✗
Composite signature
Why it's wrong here
Incorrect. Composite signatures require multiple conditions or packets to trigger.
✓
Atomic signature
Why this is correct
Correct. An atomic signature triggers on a single packet or string pattern.
Related concept
Read the scenario before looking for a memorised answer.
✗
Anomaly signature
Why it's wrong here
Incorrect. Anomaly signatures detect deviations from baseline behavior, not a specific string.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between atomic and stateful signatures by presenting a single-packet pattern and expecting candidates to recognize that no session tracking is involved, leading some to mistakenly choose 'stateful' because they associate '/etc/passwd' with a multi-step exploit.
Detailed technical explanation
How to think about this question
Atomic signatures are often implemented as simple pattern-matching rules in engines like Snort or Suricata, using the 'content' keyword. For example, 'alert tcp any any -> any any (content:"/etc/passwd"; sid:1000001;)' triggers on any TCP packet containing that string, regardless of context. In real-world scenarios, this can generate false positives if the string appears in legitimate traffic (e.g., HTTP requests to a help page), so analysts often pair atomic signatures with additional filters like 'flow:to_server,established' to reduce noise.
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.
TExam Day Tips
→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 small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Network Intrusion Analysis — This question tests Network Intrusion Analysis — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Atomic signature — The string '/etc/passwd' is a single, fixed pattern that the IDS matches against a single packet payload. This is the definition of an atomic signature: it looks for a specific content string without requiring any state or context from previous packets. Option C is correct because the alert is triggered solely by the presence of that literal string in a packet, not by any sequence of events or statistical deviation.
What should I do if I get this 200-201 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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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