Quick Answer
The correct choice is full disk encryption (FDE) on the storage device because it encrypts the entire drive at the block level, covering the operating system, applications, and all data sectors. Unlike file-level or folder-level encryption, FDE ensures that without the decryption key or passphrase, every bit of data remains unreadable even if the physical drive is removed and analyzed. On the CompTIA SecurityX CAS-004 exam, this scenario tests your understanding of data-at-rest protection versus access controls; a common trap is confusing FDE with file-level encryption or self-encrypting drives that still require proper key management. Remember that FDE’s strength lies in its transparency and full-sector coverage—it locks the whole drive, not just individual files. Memory tip: “Full disk, full stop” for stolen devices.
This CAS-004 practice question tests your understanding of security engineering. 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.
An organization wants to implement a solution that ensures data cannot be read if a storage device is physically stolen. Which encryption approach BEST meets this requirement?
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.
Transport Layer Security (TLS) for network traffic
Why wrong: Protects data in transit, not at rest.
File-level encryption on sensitive documents
Why wrong: Does not cover all data on the device.
Database column-level encryption for stored data
Why wrong: Only encrypts specific database fields, not the entire device.
Full disk encryption (FDE) on the storage device
Encrypts all data on the device, protecting against physical theft.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Full disk encryption (FDE) on the storage device
Full disk encryption (FDE) encrypts the entire storage device at the block level, including the operating system, applications, and all data. If the device is physically stolen, the data remains unreadable without the decryption key or passphrase, as the encryption is transparent and covers all sectors of the drive. This directly addresses the requirement of protecting data at rest on a stolen storage device.
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.
Transport Layer Security (TLS) for network traffic
Why it's wrong here
Protects data in transit, not at rest.
File-level encryption on sensitive documents
Why it's wrong here
Does not cover all data on the device.
Database column-level encryption for stored data
Why it's wrong here
Only encrypts specific database fields, not the entire device.
Full disk encryption (FDE) on the storage device
Why this is correct
Encrypts all data on the device, protecting against physical theft.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Cisco often tests the distinction between encryption of data in transit (TLS) and encryption of data at rest (FDE), leading candidates to mistakenly choose a network encryption solution when the question explicitly involves a stolen storage device.
Detailed technical explanation
Full disk encryption (FDE) typically operates at the block level, using algorithms like AES-256 (e.g., BitLocker with AES-XTS, LUKS with AES-CBC-ESSIV) to encrypt every sector of the disk. The decryption key is stored in a Trusted Platform Module (TPM) or derived from a pre-boot authentication password; without it, the encrypted data appears as random noise. In a real-world scenario, an attacker who steals a laptop with FDE enabled cannot boot the OS or extract data without the key, even by connecting the drive to another system.
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 CAS-004 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 exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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FAQ
Security Engineering — This question tests Security Engineering — Read the scenario before looking for a memorised answer..
The correct answer is: Full disk encryption (FDE) on the storage device — Full disk encryption (FDE) encrypts the entire storage device at the block level, including the operating system, applications, and all data. If the device is physically stolen, the data remains unreadable without the decryption key or passphrase, as the encryption is transparent and covers all sectors of the drive. This directly addresses the requirement of protecting data at rest on a stolen storage device.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 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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