Inspection of Outbound TLS Traffic is Enabled on Azure Firewall

Overview

Azure Firewall Premium offers Transport Layer Security (TLS) inspection to decrypt and inspect outbound and east-west TLS traffic, and inbound TLS traffic when used with Azure Application Gateway. TLS inspection is critical for detecting advanced threats that use encrypted channels to evade traditional security controls.

When TLS inspection is enabled, Azure Firewall uses a customer-provided CA certificate stored in Azure Key Vault to decrypt, inspect, and then re-encrypt traffic before forwarding it to its destination. This enables advanced security capabilities such as IDPS and URL filtering to analyze encrypted traffic and identify malicious activity that would otherwise remain hidden.

This check verifies that Azure Firewall Premium has TLS inspection enabled. Without TLS inspection, the firewall cannot inspect encrypted payloads, significantly limiting visibility into threats that leverage TLS to evade detection.

Remediation

• Azure Firewall Premium features implementation guide
• Deploy and configure Enterprise CA certificates for Azure Firewall
• Azure Firewall Premium certificates

Run it

The check runs as part of the whole assessment, with the ZeroTrustAssessment module installed:

Install-Module ZeroTrustAssessment -Scope CurrentUser
Connect-Maester
Invoke-Maester -Pack ZTA -SkipBuiltIn

Leave out -SkipBuiltIn to run Maester’s own checks in the same run.

About this check

Severity	High
Effort to fix	Low
Impact on users	Low
Pillar	Network
Category	Azure Network Security
Product	Azure
Feature	Network security
Area	Infrastructure hardening
ATT&CK	T1573 Encrypted Channel, T1071.001 Web Protocols
Licence	Azure_Firewall_Premium
Tenant	Workforce, External

Product, feature, area and ATT&CK are Maester’s: the assessment does not record them, so Maester keeps them in the pack’s taxonomy.json.

A Microsoft check, part of the Zero Trust Assessment pack. Text from ZeroTrustAssessment 3.1.0, © Microsoft, MIT licence.