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Detection rules › Kusto

GCP IAM - Empty user agent

Status
available
Severity
medium
Time window
1h
Source
github.com/Azure/Azure-Sentinel

'Detects requests where user agent is empty.'

MITRE ATT&CK coverage

TacticTechniques
Lateral MovementT1550 Use Alternate Authentication Material

Rule body kusto

id: 9e0d8632-d33d-4075-979e-c972674f77b3
name: GCP IAM - Empty user agent
description: |
  'Detects requests where user agent is empty.'
severity: Medium
status: Available
requiredDataConnectors:
  - connectorId: GCPIAMDataConnector
    dataTypes:
      - GCP_IAM
queryFrequency: 1h
queryPeriod: 1h
triggerOperator: gt
triggerThreshold: 0
tactics:
  - DefenseEvasion
relevantTechniques:
  - T1550
query: |
  GCP_IAM
  | where isempty(HttpUserAgentOriginal)
  | extend AccountName = tostring(split(PayloadAuthenticationinfoPrincipalemail, "@")[0]), AccountUPNSuffix = tostring(split(PayloadAuthenticationinfoPrincipalemail, "@")[1])
entityMappings:
  - entityType: Account
    fieldMappings:
      - identifier: FullName
        columnName: PayloadAuthenticationinfoPrincipalemail
      - identifier: Name
        columnName: AccountName
      - identifier: UPNSuffix
        columnName: AccountUPNSuffix
  - entityType: IP
    fieldMappings:
      - identifier: Address
        columnName: SrcIpAddr
version: 1.0.1
kind: Scheduled

Stages and Predicates

Stage 1: source

GCP_IAM

Stage 2: where

| where isempty(HttpUserAgentOriginal)

Stage 3: extend

| extend AccountName = tostring(split(PayloadAuthenticationinfoPrincipalemail, "@")[0]), AccountUPNSuffix = tostring(split(PayloadAuthenticationinfoPrincipalemail, "@")[1])

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

FieldKindValues
HttpUserAgentOriginalis_null
  • (no value, null check)

Output fields

Fields the rule emits when it matches. Chronicle authors list these in the outcome block; they appear on the detection and $risk_score drives alerting. Sentinel / Defender XDR rules build them up through project / summarize / extend stages. Sentinel maps these into alert fields via entityMappings and customDetails; Defender XDR custom detections surface them as alert fields directly.

FieldSource
AccountNameextend
AccountUPNSuffixextend