The answer is Out-of-band SQL injection, along with In-band SQL injection and Blind SQL injection, which are the three primary types of SQL injection attacks recognized on the CEH exam. Out-of-band attacks rely on a different communication channel—such as DNS or HTTP requests—to exfiltrate data when the database cannot return results directly or synchronously, making it distinct from the other two categories. On the Certified Ethical Hacker exam, this classification tests your ability to distinguish between attack vectors based on how data is retrieved: in-band uses the same channel for attack and results, blind relies on inferential responses like boolean or time-based triggers, and out-of-band uses an alternative channel. A common trap is confusing blind SQL injection with out-of-band, but remember that blind attacks still use the primary response channel for inference, whereas out-of-band requires a separate protocol. Memory tip: think "Same, Side, Silent" for In-band, Out-of-band, and Blind.
CEH Web Application and Injection Attacks Practice Question
This CEH practice question tests your understanding of web application and injection attacks. 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.
Which THREE of the following are types of SQL injection attacks? (Select 3)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Blind SQL injection (boolean-based, time-based)
Option C is correct because blind SQL injection is a recognized type of SQL injection attack where the attacker does not receive direct error messages or data from the database but instead infers information by observing the application's response (boolean-based) or by causing time delays (time-based). This technique is commonly used when the application is configured to suppress error output, forcing the attacker to rely on side-channel behaviors.
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.
✗
DOM-based SQL injection
Why it's wrong here
DOM-based is a type of XSS, not SQL injection.
✗
Stored SQL injection
Why it's wrong here
Stored is a type of XSS; SQL injection is categorized by technique.
✓
Blind SQL injection (boolean-based, time-based)
Why this is correct
Blind infers results without direct output.
Related concept
Read the scenario before looking for a memorised answer.
✓
In-band SQL injection (error-based, union-based)
Why this is correct
In-band uses the same channel to launch and retrieve results.
Related concept
Read the scenario before looking for a memorised answer.
✓
Out-of-band SQL injection
Why this is correct
Out-of-band uses a different channel (e.g., DNS, HTTP) to exfiltrate data.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse 'DOM-based' (an XSS attack) with a SQL injection type, or mistakenly think 'Stored SQL injection' is a primary category, when the CEH exam strictly recognizes in-band, blind, and out-of-band as the three main types of SQL injection attacks.
Detailed technical explanation
How to think about this question
Blind SQL injection often uses functions like `SLEEP()` in MySQL or `WAITFOR DELAY` in Microsoft SQL Server to introduce time-based delays, allowing the attacker to infer true/false conditions bit by bit. In boolean-based blind injection, the attacker crafts queries that cause different application responses (e.g., 'Welcome' vs. 'Error') based on a condition, enabling data extraction one character at a time. Real-world scenarios include exploiting login forms or search fields where error messages are hidden, requiring the attacker to use automated tools like sqlmap to perform blind injection efficiently.
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.
Web Application and Injection Attacks — This question tests Web Application and Injection Attacks — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Blind SQL injection (boolean-based, time-based) — Option C is correct because blind SQL injection is a recognized type of SQL injection attack where the attacker does not receive direct error messages or data from the database but instead infers information by observing the application's response (boolean-based) or by causing time delays (time-based). This technique is commonly used when the application is configured to suppress error output, forcing the attacker to rely on side-channel behaviors.
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
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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 penetration tester attempts a SQL injection on a login form and receives no error messages, but notices a delay in the server response when injecting ' OR SLEEP(5)--. Which type of SQL injection is this?
medium
A.Union-based SQL injection
B.Boolean-based blind SQL injection
✓ C.Time-based blind SQL injection
D.Error-based SQL injection
Why C: Time-based blind SQL injection relies on inducing a time delay to infer the truth of a condition, as no error or data is returned.
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Question Discussion
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