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CEH Enumeration and System Hacking Practice Question
This CEH practice question tests your understanding of enumeration and system hacking. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 penetration tester wants to enumerate user accounts on a Linux system running SMTP service. Which commands are commonly used for this purpose?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
VRFY, EXPN, RCPT TO
The VRFY command verifies whether a user mailbox exists on the SMTP server, EXPN expands a mailing list or alias to reveal individual member addresses, and RCPT TO specifies the recipient for a mail message and can be used to validate addresses during the SMTP conversation. These three commands are the standard SMTP enumeration techniques for discovering valid user accounts on a Linux system running an SMTP service.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse SMTP enumeration commands (VRFY, EXPN, RCPT TO) with SMTP session commands (HELO, MAIL FROM, DATA) or with authentication commands (AUTH LOGIN, STARTTLS), leading them to select options that are valid SMTP commands but not designed for user enumeration.
Detailed technical explanation
How to think about this question
Under the hood, VRFY and EXPN are defined in RFC 821 and RFC 5321 as optional SMTP commands; many modern SMTP servers disable them by default to prevent information leakage, but they remain a classic enumeration vector when enabled. RCPT TO, while mandatory for mail delivery, can be used in a brute-force manner by sending multiple RCPT TO commands with different usernames and observing the server's response codes (250 for valid, 550 for invalid) to enumerate accounts without actually sending a message.
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.
What to study next
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FAQ
Questions learners often ask
What does this CEH question test?
Enumeration and System Hacking — This question tests Enumeration and System Hacking — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: VRFY, EXPN, RCPT TO — The VRFY command verifies whether a user mailbox exists on the SMTP server, EXPN expands a mailing list or alias to reveal individual member addresses, and RCPT TO specifies the recipient for a mail message and can be used to validate addresses during the SMTP conversation. These three commands are the standard SMTP enumeration techniques for discovering valid user accounts on a Linux system running an SMTP service.
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.
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Last reviewed: Jun 24, 2026
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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