- A
Apply a regular expression that validates the Luhn algorithm in addition to pattern matching
Combining regex with Luhn check reduces false positives by verifying the mathematical validity of the number.
- B
Hash all outbound emails and compare against a database of known credit card hashes
Why wrong: Hashing makes it impossible to detect variations or new numbers, and the DLP would block legitimate emails with hash matches.
- C
Use a simple regular expression matching patterns like '\d{4}-\d{4}-\d{4}-\d{4}'
Why wrong: Simple regex can match non-credit-card number sequences, leading to high false positives.
- D
Rely on machine learning classifiers trained on past credit card data
Why wrong: Machine learning may not be as accurate for structured numeric data and requires continuous retraining.
Quick Answer
The answer is to apply a regular expression that validates the Luhn algorithm in addition to pattern matching. This is the best approach because the Luhn algorithm performs a mathematical checksum verification on the digit sequence, ensuring that only structurally valid credit card numbers are flagged, rather than every random string that matches a credit card pattern. For the CISSP exam, this question tests your understanding of data loss prevention (DLP) credit card detection techniques and how to balance detection accuracy with minimizing false positives. A common trap is assuming simple pattern matching alone is sufficient, but that would flag many harmless number sequences. The key insight is that DLP solutions for financial data must combine pattern recognition with algorithmic validation to confirm the number is mathematically plausible. Memory tip: think of the Luhn algorithm as the “last digit check” — it validates the checksum, so you don’t cry wolf over random digits.
CISSP Asset Security Practice Question
This CISSP practice question tests your understanding of asset security. 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.
A financial institution is implementing a data loss prevention (DLP) solution to protect customer financial information. The DLP system must detect and block the transmission of credit card numbers via email. Which of the following is the BEST approach to ensure accurate detection while minimizing false positives?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"best"Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
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
Apply a regular expression that validates the Luhn algorithm in addition to pattern matching
Option A is correct because combining a regular expression for credit card number patterns with Luhn algorithm validation significantly reduces false positives. The Luhn algorithm checks the mathematical validity of the number (e.g., checksum), ensuring that random digit sequences matching the pattern are not flagged as credit card numbers. This dual-layer approach is a standard DLP best practice for accurately detecting sensitive data like credit card numbers.
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.
- ✓
Apply a regular expression that validates the Luhn algorithm in addition to pattern matching
Why this is correct
Combining regex with Luhn check reduces false positives by verifying the mathematical validity of the number.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Hash all outbound emails and compare against a database of known credit card hashes
Why it's wrong here
Hashing makes it impossible to detect variations or new numbers, and the DLP would block legitimate emails with hash matches.
- ✗
Use a simple regular expression matching patterns like '\d{4}-\d{4}-\d{4}-\d{4}'
Why it's wrong here
Simple regex can match non-credit-card number sequences, leading to high false positives.
- ✗
Rely on machine learning classifiers trained on past credit card data
Why it's wrong here
Machine learning may not be as accurate for structured numeric data and requires continuous retraining.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may choose option C, thinking simple pattern matching is sufficient, but they overlook the need for Luhn validation to avoid false positives from non-credit-card digit sequences.
Detailed technical explanation
How to think about this question
The Luhn algorithm (also known as mod 10) works by doubling every second digit from the right, summing all digits, and checking if the total is divisible by 10. In DLP systems, this validation is applied after pattern matching to confirm the number is a valid credit card number, not just a random digit string. Real-world DLP solutions like Symantec or McAfee often use this combined approach to balance detection accuracy with low false positive rates, especially in high-volume email environments.
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 security analyst at a medium-sized enterprise encounters this scenario during an investigation or architecture review. The correct answer reflects best practice for the specific threat or control described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Security exam questions test whether you can match controls to threats in context — not just recall definitions.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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FAQ
Questions learners often ask
What does this CISSP question test?
Asset Security — This question tests Asset Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Apply a regular expression that validates the Luhn algorithm in addition to pattern matching — Option A is correct because combining a regular expression for credit card number patterns with Luhn algorithm validation significantly reduces false positives. The Luhn algorithm checks the mathematical validity of the number (e.g., checksum), ensuring that random digit sequences matching the pattern are not flagged as credit card numbers. This dual-layer approach is a standard DLP best practice for accurately detecting sensitive data like credit card numbers.
What should I do if I get this CISSP 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: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
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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Last reviewed: Jun 24, 2026
This CISSP practice question is part of Courseiva's free ISC2 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 CISSP exam.
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