Azure Firewall Premium is worth evaluating when your network controls need to inspect supported encrypted traffic or detect threats with IDPS. Buying the tier is only the first step. Routing, certificate trust, policy tuning, and useful logging determine what protection you actually get.
Start with the traffic path
Workload → intended route → Azure Firewall policy → destination
Check the return path as well. A correctly configured inspection policy cannot protect traffic that bypasses the firewall.
Standard already supports application-level FQDN filtering; it is not limited to IP addresses and ports. Premium adds capabilities including TLS inspection, IDPS, and full URL filtering. Select the tier based on the controls your workload needs, rather than a blanket rule for an entire industry.
TLS inspection needs a certificate plan
For supported TLS inspection, the firewall decrypts traffic, inspects it, and establishes a separate encrypted connection onward. Azure Firewall Premium uses an intermediate CA certificate stored in Key Vault. Clients must trust the appropriate issuing chain.
Document certificate ownership, expiry monitoring, rotation, and the firewall’s access to the certificate. Test applications with certificate pinning or custom trust stores before rollout. Record justified inspection exceptions with owners and review dates.
Tune IDPS with representative traffic
IDPS uses Microsoft-managed signatures. Begin a controlled rollout in Alert mode, inspect matches, and move suitable coverage to Alert and Deny after validation. Choose the observation period around business traffic, including batch jobs and infrequent integrations.
Do not exempt a signature solely because you run the affected service. Investigate the match and narrow any exception to the evidence. Use supported signature overrides and bypass controls; do not assume the service accepts arbitrary custom detection signatures.
Use URL controls deliberately
Use URL filtering when the path matters, and web categories when a broader policy is appropriate. Test both allowed and denied examples. Classification and business needs change, so category-based rules still require review.
Make logs useful
Enable the diagnostic categories needed for operations and investigation, and validate their arrival in your monitoring workspace. Correlate firewall events with application and identity evidence where possible, without treating a correlation alone as proof of compromise.
For a lab exercise, generate a permitted request, a policy-denied request, and a safe documented IDPS test. Check the source, destination, action, and rule in the resulting records. Assign an owner to alert triage and monitor ingestion gaps.
Rollout checklist and trade-offs
Validate routing and DNS. Confirm client certificate trust. Test business applications and bypass requirements. Tune IDPS. Review logging costs and retention. Measure latency and throughput. Keep an approved rollback plan. Expand the rollout only after application owners accept the test results.
Inspection adds operational work and can affect compatibility and performance. A narrow, tested policy is easier to maintain than a broad deployment with poorly understood exceptions.
Microsoft documentation
Deploy and test Azure Firewall Premium
TLS inspection certificate requirements
Secure an Azure Firewall deployment
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