Encrypting both the email body and the attachment is the correct control because SMTP transmits data in plaintext by default, meaning any email marked Confidential—including its spreadsheet attachment—can be intercepted and read without encryption. This technical reality, rooted in RFC 5321, directly addresses the need for confidentiality of sensitive data in transit. On the CISSP exam, this scenario tests your understanding of asset security and the distinction between data at rest and data in transit; a common trap is assuming that SMTP itself provides encryption, or that encrypting only the attachment is sufficient. Remember the memory tip: “SMTP sends in the clear—encrypt the whole envelope, not just the letter.”
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.
Exhibit
Data classification labels: Public, Internal, Confidential, Highly Confidential. Handling: Confidential data must be encrypted at rest and in transit. Access limited to employees with business need.
Refer to the exhibit. A project team is sending a spreadsheet marked Confidential via email. What control is required?
Data classification labels: Public, Internal, Confidential, Highly Confidential. Handling: Confidential data must be encrypted at rest and in transit. Access limited to employees with business need.
A
Both A and B
Why wrong: While both encrypt, the policy requires encryption in transit; email encryption is sufficient.
B
Encrypt the email and attachment
Email encryption protects the data in transit as policy requires.
C
No additional controls if sent over internal network
Why wrong: Internal network does not exempt from encryption requirement per policy.
D
Use a secure file transfer protocol
Why wrong: This is also encryption but may not be the immediate action for email.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Encrypt the email and attachment
Option B is correct because email transmissions, including attachments, are transmitted in plaintext by default using SMTP (RFC 5321). Encrypting both the email body and the attachment ensures confidentiality, protecting the spreadsheet marked Confidential from unauthorized access during transit. This aligns with the principle of protecting data at rest and in transit as required by asset security policies.
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.
✗
Both A and B
Why it's wrong here
While both encrypt, the policy requires encryption in transit; email encryption is sufficient.
✓
Encrypt the email and attachment
Why this is correct
Email encryption protects the data in transit as policy requires.
Related concept
Read the scenario before looking for a memorised answer.
✗
No additional controls if sent over internal network
Why it's wrong here
Internal network does not exempt from encryption requirement per policy.
✗
Use a secure file transfer protocol
Why it's wrong here
This is also encryption but may not be the immediate action for email.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume internal networks are safe or that secure file transfer protocols are equivalent to email encryption, but CISSP tests the specific requirement to protect data in transit over any network, including internal ones, using appropriate cryptographic controls like email encryption.
Detailed technical explanation
How to think about this question
Email encryption typically relies on S/MIME (using X.509 certificates) or PGP/MIME (using public-key cryptography) to encrypt the message body and attachments. Without encryption, SMTP traffic can be captured in transit using tools like Wireshark, and even on internal networks, protocols like SMTP are often unencrypted unless STARTTLS is enforced. A real-world scenario is a data breach where an internal email containing confidential spreadsheets was intercepted via a compromised switch, highlighting that network perimeter controls are insufficient without encryption.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CISSP question in full detail.
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: Encrypt the email and attachment — Option B is correct because email transmissions, including attachments, are transmitted in plaintext by default using SMTP (RFC 5321). Encrypting both the email body and the attachment ensures confidentiality, protecting the spreadsheet marked Confidential from unauthorized access during transit. This aligns with the principle of protecting data at rest and in transit as required by asset security policies.
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.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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