The correct answer is encryption at the network layer, specifically using IPsec. This control directly prevents traffic interception because IPsec operates at Layer 3, encrypting the entire IP packet—including the payload and headers—so that even if an attacker captures the data stream, the contents remain unreadable without the decryption keys. On the CISSP exam, this scenario tests your understanding of the OSI model and where encryption must be applied to protect data in transit; a common trap is confusing IPsec with TLS, which only encrypts at the transport layer (Layer 4) and leaves IP headers exposed. Remember that IPsec can run in transport mode for host-to-host encryption or tunnel mode for VPNs, making it the go-to for network layer encryption to prevent interception. A useful memory tip: “IPsec secures the whole packet, TLS only the payload.”
CISSP Communication and Network Security Practice Question
This CISSP practice question tests your understanding of communication and network security. 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.
A company recently suffered a data breach where an attacker was able to intercept network traffic and read sensitive data. Which network security control should be implemented to prevent this type of attack?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Encryption at the network layer (e.g., IPsec)
IPsec operates at the network layer (Layer 3) and provides encryption of the entire IP packet, including the payload, ensuring that even if an attacker intercepts the traffic, the data remains unreadable. This directly addresses the scenario where an attacker reads sensitive data from intercepted network traffic, as IPsec can be configured in transport mode for end-to-end encryption or tunnel mode for VPNs.
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.
✓
Encryption at the network layer (e.g., IPsec)
Why this is correct
IPsec encrypts IP packets, making intercepted data unreadable without decryption keys.
Related concept
Read the scenario before looking for a memorised answer.
✗
Network segmentation
Why it's wrong here
Segmentation limits the blast radius but does not encrypt traffic; an attacker on the same segment could still intercept.
✗
Intrusion prevention system (IPS)
Why it's wrong here
IPS can detect and block certain attacks but does not encrypt traffic; prevention of interception requires encryption.
✗
Strong password policies
Why it's wrong here
Strong passwords authenticate users but do not protect data in transit from sniffing.
Common exam traps
Common exam trap: answer the scenario, not the keyword
ISC2 often tests the misconception that network segmentation (Option B) prevents data interception, but segmentation only limits lateral movement, not the ability to read traffic within the same segment.
Detailed technical explanation
How to think about this question
IPsec uses the Authentication Header (AH) and Encapsulating Security Payload (ESP) protocols; ESP provides encryption and optional authentication, while AH only provides integrity. In transport mode, IPsec encrypts only the payload (not the IP header), which is suitable for host-to-host communication, while tunnel mode encrypts the entire original IP packet, adding a new header—commonly used in site-to-site VPNs. A subtle behavior is that IPsec can be vulnerable to IKE (Internet Key Exchange) protocol attacks if weak pre-shared keys or outdated Diffie-Hellman groups are used, so proper key management (RFC 7296) is critical.
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 developer is choosing between AES-256 (symmetric) and RSA-2048 (asymmetric) for encrypting a large file that will be sent to a partner. Symmetric encryption is fast but requires key exchange; asymmetric is slower but solves the key distribution problem. A hybrid approach — encrypt the file with AES, encrypt the AES key with RSA — is standard. Questions like this test whether you understand when each approach applies.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CISSP question in full detail.
Communication and Network Security — This question tests Communication and Network Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Encryption at the network layer (e.g., IPsec) — IPsec operates at the network layer (Layer 3) and provides encryption of the entire IP packet, including the payload, ensuring that even if an attacker intercepts the traffic, the data remains unreadable. This directly addresses the scenario where an attacker reads sensitive data from intercepted network traffic, as IPsec can be configured in transport mode for end-to-end encryption or tunnel mode for VPNs.
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.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
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.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.