The answer is the network firewall, along with a Virtual Private Network (VPN) and an Intrusion Detection System (IDS). These three are considered network security controls because they operate at the network layer to monitor, filter, or secure traffic between segments. A firewall enforces access rules based on IP addresses and ports, a VPN encrypts data in transit using protocols like IPsec to ensure confidentiality and integrity, and an IDS inspects packets for malicious signatures or anomalies. On the ISC2 Certified in Cybersecurity CC exam, this question tests your ability to distinguish network-layer controls from host-based or administrative controls, with a common trap being to select an antivirus or a security policy instead. Remember the mnemonic “FIV” for Firewall, IDS, VPN—these three directly manage traffic on the wire, while other options often protect endpoints or define rules rather than enforce them at the network level.
ISC2 CC Network Security Practice Question
This CC practice question tests your understanding of network 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.
A network administrator is implementing a defense-in-depth strategy. Which THREE of the following are considered network security controls? (Select THREE)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Virtual Private Network (VPN)
A Virtual Private Network (VPN) is a network security control because it creates an encrypted tunnel (using protocols such as IPsec or TLS) between a remote user and the corporate network, ensuring data confidentiality and integrity over untrusted networks like the internet. This protects data in transit and authenticates endpoints, which is a core network-layer security function.
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.
✓
Virtual Private Network (VPN)
Why this is correct
VPN provides encrypted tunnels for secure communication over untrusted networks, a network security control.
Related concept
Read the scenario before looking for a memorised answer.
✓
Intrusion Detection System (IDS)
Why this is correct
IDS monitors network traffic for malicious activity, making it a network security control.
Related concept
Read the scenario before looking for a memorised answer.
✗
Full disk encryption
Why it's wrong here
Full disk encryption protects data at rest on endpoints, not the network.
✓
Network firewall
Why this is correct
A network firewall filters traffic between networks and is a fundamental network security control.
Related concept
Read the scenario before looking for a memorised answer.
✗
Antivirus software
Why it's wrong here
Antivirus is an endpoint security control, not a network control.
Common exam traps
Common exam trap: answer the scenario, not the keyword
ISC2 often tests the distinction between network-layer controls (VPN, IDS, firewall) and host/endpoint controls (disk encryption, antivirus), so the trap is that candidates mistakenly classify host-based security measures as network security controls.
Detailed technical explanation
How to think about this question
VPNs rely on tunneling protocols such as IPsec (using IKE for key exchange and ESP for encryption) or TLS/DTLS for SSL VPNs. A subtle behavior is that VPNs can be configured in split-tunnel mode, where only corporate-bound traffic traverses the encrypted tunnel while internet traffic goes directly, which reduces bandwidth but can introduce security risks if the remote host is compromised. In a real-world scenario, a VPN is essential for secure remote access to internal resources like a database server, but it does not inspect traffic for threats—that is the role of an IDS/IPS or firewall.
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 CC question in full detail.
Network Security — This question tests Network Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Virtual Private Network (VPN) — A Virtual Private Network (VPN) is a network security control because it creates an encrypted tunnel (using protocols such as IPsec or TLS) between a remote user and the corporate network, ensuring data confidentiality and integrity over untrusted networks like the internet. This protects data in transit and authenticates endpoints, which is a core network-layer security function.
What should I do if I get this CC 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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