- A
Implement VLANs with ACLs to separate departments and restrict traffic between them.
VLANs create logical segmentation; ACLs enforce policies to allow only necessary traffic, containing outbreaks to one segment.
- B
Enable full-disk encryption on all endpoints and servers.
Why wrong: Encryption protects data if a device is lost or stolen but does not prevent malware from spreading across the network.
- C
Upgrade all endpoint antivirus to the latest version and enable real-time scanning.
Why wrong: Antivirus can detect known malware but does not contain lateral movement; a zero-day or fast-spreading ransomware may bypass it.
- D
Deploy a network-based intrusion detection system (IDS) to alert on suspicious traffic.
Why wrong: IDS only detects and alerts; it does not actively block lateral movement, so an outbreak can still spread.
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 small company with 50 employees operates a flat network where all workstations, servers, and printers are on a single subnet without segmentation. The company recently suffered a ransomware outbreak that spread rapidly from an infected workstation to the file server and multiple other machines, causing significant downtime. The IT manager wants to redesign the network to contain future outbreaks and limit lateral movement. The budget is limited, and the environment uses a mixture of managed and unmanaged switches. Which course of action would BEST mitigate the risk of lateral spread while minimizing cost and complexity?
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
Implement VLANs with ACLs to separate departments and restrict traffic between them.
Implementing VLANs with ACLs segments the flat network into separate broadcast domains, preventing lateral movement by restricting traffic between departments at Layer 2. This directly contains ransomware propagation without requiring new hardware, as VLANs can be configured on existing managed switches, making it cost-effective. ACLs further enforce least-privilege access between VLANs, blocking unauthorized inter-VLAN communication.
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.
- ✓
Implement VLANs with ACLs to separate departments and restrict traffic between them.
Why this is correct
VLANs create logical segmentation; ACLs enforce policies to allow only necessary traffic, containing outbreaks to one segment.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Enable full-disk encryption on all endpoints and servers.
Why it's wrong here
Encryption protects data if a device is lost or stolen but does not prevent malware from spreading across the network.
- ✗
Upgrade all endpoint antivirus to the latest version and enable real-time scanning.
Why it's wrong here
Antivirus can detect known malware but does not contain lateral movement; a zero-day or fast-spreading ransomware may bypass it.
- ✗
Deploy a network-based intrusion detection system (IDS) to alert on suspicious traffic.
Why it's wrong here
IDS only detects and alerts; it does not actively block lateral movement, so an outbreak can still spread.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often choose endpoint-focused solutions (like antivirus or encryption) because they seem directly related to malware, but the question specifically targets lateral movement containment, which requires network segmentation, not just endpoint protection.
Detailed technical explanation
How to think about this question
VLANs operate at Layer 2 by tagging frames with 802.1Q headers, isolating traffic into separate broadcast domains; inter-VLAN routing requires a Layer 3 device (e.g., router or Layer 3 switch) where ACLs can filter based on source/destination IP and port. In a flat network, ransomware exploits unsegmented broadcast domains to propagate via SMB (port 445) or RDP (port 3389); VLANs force all cross-subnet traffic through a controlled routing point, enabling ACLs to block these ports between segments. Real-world example: a hospital isolates IoT devices from patient records VLAN to prevent malware from jumping to critical systems.
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.
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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Communication and Network Security — study guide chapter
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FAQ
Questions learners often ask
What does this CISSP question test?
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: Implement VLANs with ACLs to separate departments and restrict traffic between them. — Implementing VLANs with ACLs segments the flat network into separate broadcast domains, preventing lateral movement by restricting traffic between departments at Layer 2. This directly contains ransomware propagation without requiring new hardware, as VLANs can be configured on existing managed switches, making it cost-effective. ACLs further enforce least-privilege access between VLANs, blocking unauthorized inter-VLAN communication.
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
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 →
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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