Quick Answer
The answer is the output of the 'id' command appearing in the response. This is the definitive symptom of a successful command injection attack because the 'id' command, when executed on a Linux or Unix system, returns the current user’s user ID (UID) and group ID (GID) without altering the system state, making it a safe, non-destructive test payload. On the Certified Ethical Hacker CEH exam, this concept tests your ability to distinguish between a reflected vulnerability and actual command execution; a common trap is confusing error messages or echoed input with injected command output. The key insight is that if you inject 'id' and see something like "uid=33(www-data)" in the HTTP response, you have confirmed remote code execution. For a quick memory tip, remember the mnemonic "ID Injects Directly" — if you see the ID, you’ve got command injection confirmed.
This CEH practice question tests your understanding of web application and injection attacks. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 of the following is a symptom of a successful command injection attack?
The server returns a 404 error
Why wrong: 404 indicates resource not found, not command execution.
The output of the 'id' command appears in the response
If the command executes, its output may be reflected.
The HTTP response header contains 'Server: Apache'
Why wrong: Server header is normal, not indicative of injection.
The page loads slower than usual
Why wrong: Slowness is not a specific indicator of injection.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
The output of the 'id' command appears in the response
Command injection allows execution of system commands; using 'id' is a common test to confirm.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
The server returns a 404 error
Why it's wrong here
404 indicates resource not found, not command execution.
The output of the 'id' command appears in the response
Why this is correct
If the command executes, its output may be reflected.
Related concept
Read the scenario before looking for a memorised answer.
The HTTP response header contains 'Server: Apache'
Why it's wrong here
Server header is normal, not indicative of injection.
The page loads slower than usual
Why it's wrong here
Slowness is not a specific indicator of injection.
Common exam traps
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Trap categories for this question
Command / output trap
404 indicates resource not found, not command execution.
Detailed technical explanation
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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
Identify which CEH exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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FAQ
Web Application and Injection Attacks — This question tests Web Application and Injection Attacks — Read the scenario before looking for a memorised answer..
The correct answer is: The output of the 'id' command appears in the response — Command injection allows execution of system commands; using 'id' is a common test to confirm.
Identify which CEH exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 21, 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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