ISC2 CC Network Security Practice Question
A financial services company is designing a demilitarized zone (DMZ) for its public web and email relay servers. The security architect wants to reduce the attack surface and limit what an attacker can reach if a DMZ host is compromised. Which two design practices should be implemented? (Choose two.)
⚠ Common exam trap
The trap here is treating the DMZ as a trusted extension of the internal network, which leads to permissive rules that allow a compromised host to pivot inward.
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
✓
Permit only the specific inbound ports required for the public services into the DMZ.
A DMZ should expose only the ports required for public services and should enforce strict, default-deny rules on the internal firewall so that a compromised DMZ host cannot freely reach internal systems. These two practices reduce attack surface and contain lateral movement. Opening management paths or sharing VLANs and rule sets with internal networks removes the separation that makes the DMZ valuable.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Allow the DMZ hosts to initiate connections to any internal server for management convenience.
Why it's wrong here
Allowing DMZ hosts to initiate connections to any internal server creates a direct path from a compromised DMZ host into the internal network, defeating the purpose of the DMZ. Management should be tightly controlled, typically from a dedicated management network with specific rules, not open to all internal servers. This practice increases risk and violates least privilege.
- ✗
Place the DMZ servers on the same VLAN as internal user workstations to simplify routing.
Why it's wrong here
Sharing a VLAN with internal workstations removes the Layer 2 boundary and allows direct communication between DMZ hosts and internal users, which is exactly what a DMZ is meant to prevent. It also exposes internal systems to broadcast traffic and attacks from the DMZ. This design would make containment nearly impossible after a compromise.
- ✓
Permit only the specific inbound ports required for the public services into the DMZ.
Why this is correct
Restricting inbound access to only the ports needed for web and email reduces the exposed attack surface and prevents attackers from reaching unnecessary services. This is a core DMZ design principle: the external firewall allows only what the public service requires, such as HTTPS for the web server and the mail relay port. It directly limits what an external attacker can probe or exploit.
- ✓
Configure the internal firewall to allow only required DMZ-to-internal traffic and deny the rest.
Why this is correct
The internal firewall should enforce a default-deny posture, permitting only the specific flows the DMZ hosts need to reach internal systems, such as database queries for the web application. This limits lateral movement if a DMZ host is compromised. It is a foundational control for containing breaches and is explicitly recommended in DMZ architectures.
- ✗
Use the same firewall rule set for both the external and internal firewalls to reduce administrative effort.
Why it's wrong here
The external and internal firewalls face different trust zones and require different policies. The external firewall controls internet-to-DMZ traffic, while the internal firewall controls DMZ-to-internal traffic. Using one rule set would either overexpose the DMZ or block legitimate service flows, and it undermines the defense-in-depth principle of separate policy enforcement points.
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Related to this question
Learn chapter
Incident Response and Management
Key term
Lateral movement
Lateral movement is the technique attackers use to move through a network from one compromised system to another, seeking sensitive data or higher privileges.
Key term
DMZ
A DMZ (demilitarized zone) is a network segment that sits between an internal private network and the public internet, hosting publicly accessible services while keeping the internal network isolated.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official ISC2 exam blueprint
This CC 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 CC exam.