CEH Footprinting, Reconnaissance and Scanning Practice Question
This CEH practice question tests your understanding of footprinting, reconnaissance and scanning. 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 runs `nmap -sS -sV -A 192.168.1.100` and obtains open ports and service versions. However, the analyst suspects the target is behind an IDS/IPS. Which Nmap technique would BEST evade detection while still performing a similar scan?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Add -f to fragment IP packets
Option A is correct because using the `-f` flag fragments the IP packets, splitting the TCP header across multiple packets. This helps evade simple IDS/IPS signatures that rely on detecting a complete SYN scan in a single packet, as the fragmented packets may bypass pattern-matching rules or reassembly buffers.
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.
✓
Add -f to fragment IP packets
Why this is correct
Fragmentation can evade simple packet inspection by IDS/IPS.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Use -sT instead of -sS to perform a full TCP connect scan
Why it's wrong here
Full connect scan is more easily detected and logged.
✗
Increase timing to -T5 for a faster scan
Why it's wrong here
Aggressive timing increases scan speed but also increases detection risk.
✗
Replace -sV with -sU to scan UDP services
Why it's wrong here
UDP scan does not help evade detection; it just scans different protocols.
Common exam traps
Common exam trap: answer the scenario, not the keyword
EC-Council often tests the misconception that faster scans (`-T5`) are stealthier, when in reality they increase noise and detection risk, while fragmentation (`-f`) is a recognized evasion technique for bypassing packet inspection.
Detailed technical explanation
How to think about this question
IP fragmentation works by splitting the TCP segment into smaller IP packets, each with its own header and fragment offset. Many IDS/IPS systems perform simple pattern matching on complete packets; fragmented packets may require reassembly before inspection, which some devices handle poorly or skip entirely. In real-world scenarios, combining fragmentation with other evasion techniques like decoy scans (`-D`) or using a slow timing template (`-T1`) can further reduce detection risk.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CEH question in full detail.
Footprinting, Reconnaissance and Scanning — This question tests Footprinting, Reconnaissance and Scanning — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Add -f to fragment IP packets — Option A is correct because using the `-f` flag fragments the IP packets, splitting the TCP header across multiple packets. This helps evade simple IDS/IPS signatures that rely on detecting a complete SYN scan in a single packet, as the fragmented packets may bypass pattern-matching rules or reassembly buffers.
What should I do if I get this CEH question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
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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