DMZ Purpose and Design

A Demilitarized Zone (DMZ) is a network segment that sits between the internal trusted network and untrusted external networks. DMZs host public-facing services like web servers, email servers, and DNS while protecting internal resources from direct internet exposure.

DMZ Topologies

Common DMZ designs include single firewall with three interfaces (external, DMZ, internal), dual firewall architecture with screening router, and multi-tier DMZ with separate zones for different service types. Topology choice depends on security requirements and available resources.

Security Rules and Policies

DMZ security requires restrictive firewall rules: deny all by default, allow only specific traffic from internet to DMZ services, strictly control DMZ to internal network access, prevent DMZ-to-DMZ lateral movement, and log all connections for monitoring.

DMZ Services Configuration

Services in the DMZ should be hardened, patched regularly, and run with minimal privileges. Implement application-level security, use separate accounts for each service, enable detailed logging, and conduct regular vulnerability assessments.

Monitoring and Maintenance

Continuous monitoring of DMZ traffic patterns, security events, and system health is essential. Implement intrusion detection, file integrity monitoring, and regular security audits to detect compromises early and maintain DMZ security posture.