Azure Function Master / API Key

Detects Azure Functions master key and API key patterns. This pattern is based on a Microsoft Purview built-in sensitive information type. Users already running Purview may prefer to enable the built-in SIT directly, or use this version as a starting point for customisation.

Type

regex

Engine

universal

Confidence

high

Confidence justification

High confidence: structurally constrained pattern with Azure Functions context keywords reduces false positive rates significantly. Added context gating and exclusion rules improve precision and reduce incidental matches.

Detection quality

Verified

Jurisdictions

global

Regulations

Criminal Code Act 1995 (Cth)

Frameworks

CIS Controls, ISO 27001, NIST CSF, PCI-DSS, SOC 2

Data categories

credentials, security

Scope

specific

Risk rating

10

Platform compatibility

Purview: Compatible, GCP DLP: Compatible, Macie: Compatible, Zscaler: Compatible, Palo Alto: Degraded, Netskope: Unsupported

Pattern

(?i)(?:x-functions-key|master[._-]?key|function[._-]?key|host[._-]?key|default[._-]?key)\s*[:=]\s*"?[A-Za-z0-9_\-]{30,60}"?

Corroborative evidence keywords

Azure Functions, function app, x-functions-key, master key, host key, function key, api key, azurewebsites.net, api_key, apikey, access key, access token, auth token, authorization, bearer, conn str, connection string, connectionstring, cookie, credential (+44 more)

Proximity: 300 characters

Should match

• x-functions-key=AAAA0000BBBB1111CCCC2222DDDD3333EEEE4444FFFF — Azure Functions host key
• master_key="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnop" — Functions master key
• function_key="000000000000000000000000000000000000000000" — Function key with placeholder value

Should not match

• x-functions-key="" — Empty key value
• functionAppName=my-function-app — Function app name, not a key
• template example placeholder record identifier — Template/sample context should be excluded even when anchor words are present

Known false positives

• Azure Functions documentation and deployment templates with placeholder keys. Mitigation: Check for common placeholder patterns and documentation context.
• API keys from other services that use similar alphanumeric formats. Mitigation: Require proximity to Azure Functions specific keywords for differentiation.

References

• Azure Function master / API key entity definition - Microsoft Learn