The answer is encryption, slow scans, and fragmentation. Encryption is a common evasion technique because it scrambles payload data, making signature-based detection tools like intrusion detection systems (IDS) and intrusion prevention systems (IPS) unable to inspect malicious content. Slow scans evade detection by sending packets at a very low rate over extended periods, staying below the threshold of time-based alerting algorithms. Fragmentation splits attack payloads into small, non-contiguous packets, forcing security devices to reassemble them before analysis, which can bypass pattern-matching rules. On the Cisco CyberOps Associate 200-201 exam, this question tests your understanding of how attackers circumvent network security controls, often appearing in the "Security Concepts" domain. A common trap is confusing encryption with simple encoding—encryption requires a key, while encoding does not. Remember the mnemonic "ESF" for Encryption, Slow scans, and Fragmentation to recall the three core evasion methods.
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.
Which THREE of the following are common evasion techniques used by attackers?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Slow scans
Slow scans are a common evasion technique used by attackers to avoid detection by intrusion detection systems (IDS) and intrusion prevention systems (IPS). By sending packets at a very low rate, often over hours or days, the scan falls below the threshold of time-based detection algorithms that trigger alerts on rapid port sweeps. This technique exploits the fact that many security devices rely on timing heuristics to identify reconnaissance activity.
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.
Read the scenario before looking for a memorised answer.
✓
Fragmentation
Why this is correct
Correct. Fragmentation is a common evasion technique to hide payload from IDS.
Related concept
Read the scenario before looking for a memorised answer.
✗
Using high ports
Why it's wrong here
Incorrect. While attackers may use high ports, it is not an evasion technique per se.
✗
Patching vulnerabilities
Why it's wrong here
Incorrect. Patching is a defensive measure, not an attack technique.
✓
Encryption
Why this is correct
Correct. Encryption obscures the content of communications.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between evasion techniques and general security practices; the trap here is that candidates may mistake 'patching vulnerabilities' as an attacker action, when in reality it is a defender's mitigation strategy, not an evasion method.
Detailed technical explanation
How to think about this question
Slow scans leverage the fact that many IDS/IPS sensors use a sliding window or rate-based threshold (e.g., more than 10 SYN packets per second) to detect port scans. By spacing packets beyond this window (e.g., one packet every 60 seconds), the scan evades these heuristics. Fragmentation works by splitting a single packet (e.g., a TCP SYN) into multiple smaller fragments, causing the IDS to miss the full header if it does not perform proper reassembly, as described in RFC 791 for IP fragmentation. Encryption, such as TLS or SSH tunneling, obfuscates the payload content, preventing signature-based detection from inspecting the actual attack data.
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: Slow scans — Slow scans are a common evasion technique used by attackers to avoid detection by intrusion detection systems (IDS) and intrusion prevention systems (IPS). By sending packets at a very low rate, often over hours or days, the scan falls below the threshold of time-based detection algorithms that trigger alerts on rapid port sweeps. This technique exploits the fact that many security devices rely on timing heuristics to identify reconnaissance activity.
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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