The answer is WHOIS lookups and using Google dorks to find exposed files. Both techniques are considered passive reconnaissance because they gather information without directly interacting with the target system—WHOIS queries rely on public third-party databases like whois.arin.net, while Google dorks leverage cached search engine results, meaning no packets are sent to the target’s own infrastructure. On the Certified Ethical Hacker CEH exam, this distinction tests your understanding of the reconnaissance phase, where passive techniques avoid alerting intrusion detection systems. A common trap is confusing active tools like Nmap or netcat with passive methods; remember that if you never touch the target’s network, it’s passive. For a quick memory tip, think “third-party sources only”—if the data comes from a public registry or a search engine cache, you’re staying passive.
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.
Which TWO of the following techniques are considered passive reconnaissance? (Select exactly 2.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Performing a WHOIS lookup
A WHOIS lookup queries public databases (e.g., whois.arin.net) to retrieve registration details for domains or IP blocks. This process does not send any packets directly to the target system; it relies on third-party servers, making it a passive reconnaissance technique.
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.
✓
Performing a WHOIS lookup
Why this is correct
WHOIS queries public databases, no direct interaction with target.
Related concept
Read the scenario before looking for a memorised answer.
✗
Connecting to a web server to grab its banner
Why it's wrong here
Connecting to a server is active.
✗
Sending ICMP echo requests to a target
Why it's wrong here
Sending packets is active reconnaissance.
✓
Using Google dorks to find exposed files
Why this is correct
Google dorks use search engine indexes, no direct contact.
Related concept
Read the scenario before looking for a memorised answer.
✗
Running a Nmap SYN scan
Why it's wrong here
Nmap SYN scan sends packets to the target, active.
Common exam traps
Common exam trap: answer the scenario, not the keyword
EC-Council often tests the distinction that any technique involving direct interaction with the target's network stack (even a single packet or connection) is active, while passive methods rely on third-party sources or pre-existing data.
Detailed technical explanation
How to think about this question
Passive reconnaissance relies on publicly available information without engaging the target's systems. WHOIS lookups use port 43 (TCP) to query WHOIS servers, while Google dorks leverage search engine caches and indexes. Under the hood, these methods never generate traffic to the target's IP, thus avoiding detection by IDS/IPS or firewall logs. In contrast, banner grabbing (option B) often uses a full TCP handshake, which is logged by the target.
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 practitioner preparing for the CEH exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
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: Performing a WHOIS lookup — A WHOIS lookup queries public databases (e.g., whois.arin.net) to retrieve registration details for domains or IP blocks. This process does not send any packets directly to the target system; it relies on third-party servers, making it a passive reconnaissance technique.
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.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. Which of the following techniques is considered PASSIVE reconnaissance?
easy
A.Ping sweeping a subnet
B.Banner grabbing with Telnet
C.Running a SYN scan with Nmap
✓ D.Performing a WHOIS lookup
Why D: WHOIS queries retrieve domain registration records from public databases like whois.iana.org or RDAP servers. Since the target server is never contacted directly — only public registries are queried — no packets are sent to the target's infrastructure, making it a purely passive reconnaissance technique.
Last reviewed: Jun 30, 2026
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This CEH practice question is part of Courseiva's free EC-Council 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 CEH exam.
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