Quick Answer
The answer is regular expression matching, as it provides the most precise and efficient method for detecting structured data like credit card numbers in outbound traffic. Regular expressions excel here because credit card numbers follow a predictable pattern—typically 16 digits grouped in fours, with a valid Luhn checksum—allowing a DLP solution to match exact sequences without the false positives that simpler keyword or dictionary-based methods would generate. On the CompTIA SecurityX CAS-004 exam, this question tests your understanding of data classification and detection techniques; a common trap is choosing “exact data matching” or “hash-based detection,” which are better for unstructured data or known files, not for variable-format numbers. Remember the memory tip: “Patterns need patterns”—structured data like credit cards demands regex, while hashing works for exact file fingerprints.
This CAS-004 practice question tests your understanding of security engineering. 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 data loss prevention (DLP) solution is being implemented to prevent sensitive data from leaving the corporate network. Which of the following is the most effective approach for detecting structured data like credit card numbers in outbound traffic?
Keyword matching
Why wrong: Keywords are too generic and may miss structured patterns.
Regular expression matching
Regular expressions can accurately match patterns like credit card number formats.
Machine learning classification
Why wrong: Machine learning is better for unstructured data and may have higher false positives.
Exact file hash matching
Why wrong: Hash matching detects known files, not data patterns.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Regular expression matching
Regular expressions can match patterns like credit card numbers, while other methods are less precise or suited for different data types.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Keyword matching
Why it's wrong here
Keywords are too generic and may miss structured patterns.
Regular expression matching
Why this is correct
Regular expressions can accurately match patterns like credit card number formats.
Related concept
Static NAT maps one inside address to one outside address.
Machine learning classification
Why it's wrong here
Machine learning is better for unstructured data and may have higher false positives.
Exact file hash matching
Why it's wrong here
Hash matching detects known files, not data patterns.
Common exam traps
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Trap categories for this question
Keyword trap
Keywords are too generic and may miss structured patterns.
Detailed technical explanation
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
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.
What to study next
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related CAS-004 NAT questions on configuration and troubleshooting.
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FAQ
Security Engineering — This question tests Security Engineering — Static NAT maps one inside address to one outside address..
The correct answer is: Regular expression matching — Regular expressions can match patterns like credit card numbers, while other methods are less precise or suited for different data types.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related CAS-004 NAT questions on configuration and troubleshooting.
Static NAT maps one inside address to one outside address.
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Last reviewed: Jun 24, 2026
This CAS-004 practice question is part of Courseiva's free CompTIA 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 CAS-004 exam.
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