Azure CDN Front Door Security Policy: The Complete Problem-Solver's Guide

Configuring azurerm cdn_frontdoor_security_policy is one of the most critical — and most frequently misconfigured — tasks in Azure infrastructure. Get it wrong and your origin is exposed. Get it right and you block threats before they reach your backend. This guide solves every common problem engineers face when securing Azure Front Door with WAF policies.

What Is a CDN Front Door Security Policy and Why Does It Matter?

An Azure CDN Front Door security policy is a logical container for Web Application Firewall (WAF) rules, rate-based rules, and request-matching conditions that govern how inbound traffic is inspected and filtered before reaching your origin.

Without a security policy attached, your Front Door still routes traffic but performs zero inspection. Any client can hit your origin endpoints directly through the Front Door edge with no threat mitigation. The security policy is what transforms a simple load balancer into a protective gateway.

Core Components

• Prevention Mode — Actively blocks requests matching defined rulesets.
• Rate-Based Rules — Triggers actions when request volume from a single client exceeds a threshold within a time window.
• Managed Rules — Microsoft-maintained rule groups covering OWASP TOP 10, common exploit kits, and bot signatures.
• Custom Rules — Define your own match conditions (URI path, query string, header, method, etc.) and associated actions.
• Bypass Rules — Define conditions under which WAF evaluation is skipped entirely.

How Do You Create a Security Policy in Terraform (Azurerm)?

The most common pain point is the Terraform deployment itself. Below is the canonical resource block and a breakdown of every required and optional field.

resource "azurerm_cdn_frontdoor_security_policy" "example" {
  name                = "security-policy-primary"
  cdn_frontdoor_id    = azurerm_cdn_frontdoor_example.id

  security_policies {
    rate_limiting {
      name     = "rate-limit-api"
      enabled  = true
      protocol {
        port     = 443
        protocol_type = "Https"
      }
      match {
        match_condition {
          match_variables {
            variable_name = "RequestBody"
          }
          operator      = "GeoMatch"
          match_values  = ["US", "GB"]
          negation_condition = false
        }
      }
      action = "Allow"
      priority = 100
    }

    managed_rule {
      name      = "DefaultDefaultRuleSet"
      type      = "Default"
      action    = "Block"
      enabled   = true
    }
  }
}

resource "azurerm_cdn_frontdoor_waf_policy" "example" {
  name                = "waf-policy-primary"
  resource_group_name = azurerm_resource_group.example.name
  mode                = "Prevention"

  rule_set {
    rule_set_type = "MWAS"
    rule_set_version = "3.0"
  }
}

Critical Fields Explained

Pre-Deployment Security Policy Checklist

Before applying your azurerm_cdn_frontdoor_security_policy to production, run through this checklist to avoid the most common failure modes.