The correct next step is to use Shodan to search for Acme Corp’s IP ranges and perform DNS enumeration to discover subdomains and mail servers. Shodan is a powerful passive reconnaissance tool that indexes banners and metadata from internet-facing devices, allowing you to identify exposed services like email servers and web applications without sending a single packet to the target. DNS enumeration, using public MX, NS, and A records, then maps subdomains and mail servers passively, fulfilling the requirement to avoid detection. On the CEH exam, this scenario tests your understanding of passive footprinting versus active scanning—a common trap is choosing an active tool like Nmap, which would trigger alerts. Remember that passive reconnaissance relies entirely on third-party data sources; Shodan and DNS records are your stealthy allies. Memory tip: “Shodan scans the internet, not the target—so you stay hidden while gathering intel.”
CEH Footprinting and Reconnaissance Practice Question
This CEH practice question tests your understanding of footprinting and reconnaissance. 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.
You are a penetration tester for a security firm. Your client, Acme Corp, has requested an external reconnaissance assessment. They have provided their primary domain 'acme.com'. You begin by performing passive footprinting using public sources. After gathering initial information, you want to identify their email servers, subdomains, and any exposed services. You also want to map their network infrastructure without directly interacting with their systems to avoid detection. Which course of action should you take next?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "primary"
Why it matters: Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use Shodan to search for Acme Corp's IP ranges and perform DNS enumeration to discover subdomains and mail servers.
Option B is correct because Shodan allows passive identification of exposed services, including email servers and subdomains, by querying its indexed data of internet-facing devices without sending any packets to Acme Corp's systems. DNS enumeration can then be performed passively using public DNS records (e.g., MX, NS, A records) to map subdomains and mail servers, fulfilling the requirement to avoid direct interaction and detection.
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.
✗
Call Acme Corp's IT help desk posing as an employee to ask about their email server configuration.
Why it's wrong here
Social engineering is active and may be unethical or illegal without consent.
✓
Use Shodan to search for Acme Corp's IP ranges and perform DNS enumeration to discover subdomains and mail servers.
Why this is correct
Shodan provides passive information on exposed services, and DNS enumeration is passive.
Clue confirmation
The clue word "primary" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Perform a traceroute to Acme Corp's web server to map the network path.
Why it's wrong here
Traceroute sends packets that can be logged, making it active reconnaissance.
✗
Run an Nmap scan against the entire IP range of Acme Corp to identify open ports and services.
Why it's wrong here
Nmap is active scanning and may trigger intrusion detection systems.
Common exam traps
Common exam trap: answer the scenario, not the keyword
EC-Council often tests the distinction between passive and active reconnaissance, and the trap here is that candidates may confuse Shodan (passive) with Nmap (active), or think traceroute is passive because it's a common network diagnostic tool.
Detailed technical explanation
How to think about this question
Shodan crawls the internet by sending probes to common ports and stores banners, allowing passive discovery of services like SMTP (port 25), IMAP (port 143), and HTTP (port 80/443) without the target knowing. DNS enumeration using tools like `dig` or `nslookup` with options like `-t ANY` or `-t MX` queries public DNS servers, which is considered passive because the target's own DNS servers are not directly contacted in a way that reveals the enumerator's intent. In real-world assessments, combining Shodan with passive DNS (e.g., SecurityTrails) can reveal subdomains and mail servers that are not indexed by search engines.
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 and Reconnaissance — This question tests Footprinting and Reconnaissance — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use Shodan to search for Acme Corp's IP ranges and perform DNS enumeration to discover subdomains and mail servers. — Option B is correct because Shodan allows passive identification of exposed services, including email servers and subdomains, by querying its indexed data of internet-facing devices without sending any packets to Acme Corp's systems. DNS enumeration can then be performed passively using public DNS records (e.g., MX, NS, A records) to map subdomains and mail servers, fulfilling the requirement to avoid direct interaction and detection.
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: "primary". Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.
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. A security analyst is tasked with performing passive reconnaissance on a target organization. Which of the following is the BEST approach to gather information about the target's technology stack without directly interacting with the target's systems?
hard
A.Engage in social engineering via phone calls
✓ B.Use Shodan to search for target infrastructure
C.Initiate a DNS zone transfer request
D.Perform a port scan with Nmap
Why B: Shodan is a search engine that indexes banners from internet-connected devices, allowing an analyst to discover a target's exposed services, open ports, and technology stack (e.g., web servers, SSH versions, IoT devices) without sending any packets to the target's systems. This makes it a purely passive reconnaissance technique, as it relies on Shodan's pre-collected data rather than direct interaction.
Variation 2. Which TWO of the following tools are commonly used for passive reconnaissance?
medium
✓ A.theHarvester
B.nmap
C.Netcat
D.Metasploit
✓ E.Shodan
Why A: theHarvester is a passive reconnaissance tool that gathers information from public sources such as search engines (Google, Bing), PGP key servers, and the Shodan API without directly interacting with the target network. It collects email addresses, subdomains, IPs, and employee names by querying publicly available data, making it a purely passive technique.
Variation 3. Which TWO of the following tools are specifically designed for footprinting and reconnaissance tasks? (Select two.)
hard
✓ A.Shodan
B.Nmap
✓ C.Maltego
D.Metasploit
E.John the Ripper
Why A: Shodan is a search engine specifically designed for footprinting and reconnaissance by scanning and indexing internet-connected devices, such as IoT devices, servers, and industrial control systems. It allows attackers to gather information about open ports, services, and banners without direct interaction with the target, making it a primary tool for passive reconnaissance in the CEH context.
Last reviewed: Jun 30, 2026
Question Discussion
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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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