Network Security Architecture Diagram

What this diagram shows

A network security architecture diagram models how defensive layers protect an organisation's infrastructure by routing traffic through firewalls, isolating public-facing servers in a demilitarised zone (DMZ), monitoring traffic with intrusion detection systems (IDS), and centralising security events in a security information and event management (SIEM) platform. The diagram shows the flow of external traffic from the internet, inbound through perimeter firewalls, into the DMZ where public services run, then conditional access to internal networks. It demonstrates how each layer observes and logs events for correlation and threat detection.

Key components

• Internet/External Network — Untrusted source of inbound and outbound traffic that the security architecture must inspect and control.
• Perimeter Firewall — Enforces network access control policies at the organisation's edge by allowing or denying traffic based on IP addresses, ports, and protocols.
• Demilitarised Zone (DMZ) — Segregated network segment hosting public-facing applications, web servers, and mail servers that are exposed to the internet but isolated from internal assets.
• Internal Firewall/Segmentation — Restricts lateral movement between the DMZ and sensitive internal networks, applying stricter rules than the perimeter firewall.
• Intrusion Detection System (IDS) — Passively monitors network traffic against signatures and anomalies to detect attack patterns and suspicious behaviour in real time.
• SIEM Platform — Aggregates and correlates security events from firewalls, IDS, and endpoints to identify coordinated attacks and generate alerts for security operations centre analysts.
• Internal Network/Data Centre — Protected zone containing databases, file servers, and business applications that should only receive authorised traffic from validated sources.

When to use it

Use this diagram when designing or documenting enterprise perimeter defence, explaining network segmentation to stakeholders, planning incident response architecture, or assessing security posture for compliance audits (PCI-DSS, ISO 27001). It is valuable during security architecture reviews, capacity planning for security appliances, or training security teams on defence-in-depth principles. This diagram suits organisations with multiple network zones and regulatory requirements for network isolation and threat detection.

Common mistakes

• Treating the DMZ as a secure zone rather than an exposed network that assumes compromise, which leads to inadequate internal network protection and lateral movement risks.
• Omitting internal firewalls or micro-segmentation between DMZ and critical systems, allowing attackers who breach public services to directly access sensitive data and applications.
• Assuming SIEM dashboards provide security without defining response procedures, alert tuning, and skilled analyst capacity, resulting in alert fatigue and missed genuine threats.

Adapting it to your system

Start by mapping your actual network zones (branch offices, cloud environments, third-party integrations) and identify which systems are internet-facing versus internal. Replace generic firewall boxes with your specific appliances (Palo Alto Networks, Fortinet, Cisco ASA). Position servers in the DMZ according to their exposure requirements: web tier in the outer zone, application tier in a second zone, database in the inner zone if needed. Connect your IDS sensors to network taps or mirror ports where they can see traffic between zones. Link SIEM connectors to firewalls, IDS, endpoints, and application logs. Add your threat intelligence feeds, API integrations, and analyst workflows to the SIEM section.