The correct answer is to configure a firewall to deny all outbound traffic from the database server except to specific authorized destinations. This is the essence of firewall egress filtering, which blocks unauthorized outbound traffic and directly prevents data exfiltration by enforcing a default-deny rule on traffic leaving the network. Unlike an intrusion detection system, which only alerts on suspicious activity, egress filtering stops the data transfer at the network layer before it reaches the unknown external IP. On the ISC2 Certified in Cybersecurity CC exam, this question tests your understanding of preventive versus detective controls, with a common trap being to choose DLP, which monitors content but lacks the network-level blocking capability of a firewall. Remember the memory tip: "Egress equals exit—if you don't allow it out, it can't leak out."
ISC2 CC Security Principles Practice Question
This CC practice question tests your understanding of security principles. 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 security team discovers that an internal database server is sending large amounts of data to an unknown external IP address. The server is not supposed to communicate externally. Which security control should be implemented to prevent such data exfiltration?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Configure a firewall to deny all outbound traffic from the database server except to specific authorized destinations
Option A is correct because a restrictive firewall egress rule blocks unauthorized outbound traffic. IDS (C) only detects, not prevent. DLP (B) monitors content but may not block at network level. VPN (D) would not stop exfiltration; it could even facilitate it.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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 a VPN for all external communications
Why it's wrong here
A VPN would encrypt traffic but not prevent the server from sending data to unauthorized hosts.
✗
Install an intrusion detection system (IDS) on the network segment
Why it's wrong here
IDS is detective, not preventive; it would alert but not block.
✓
Configure a firewall to deny all outbound traffic from the database server except to specific authorized destinations
Why this is correct
Egress filtering blocks unauthorized outbound connections, preventing data exfiltration.
Related concept
Static NAT maps one inside address to one outside address.
✗
Deploy a data loss prevention (DLP) system on the server
Why it's wrong here
DLP can detect sensitive data but may not block all exfiltration at the network level.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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. NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated. 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 CC question in full detail.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related CC NAT questions on configuration and troubleshooting.
Security Principles — This question tests Security Principles — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Configure a firewall to deny all outbound traffic from the database server except to specific authorized destinations — Option A is correct because a restrictive firewall egress rule blocks unauthorized outbound traffic. IDS (C) only detects, not prevent. DLP (B) monitors content but may not block at network level. VPN (D) would not stop exfiltration; it could even facilitate it.
What should I do if I get this CC question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related CC NAT questions on configuration and troubleshooting.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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