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Detection rules › Kusto

OCI - Unexpected user agent

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

'Detects unexpected user agent strings.'

MITRE ATT&CK coverage

TacticTechniques
Initial AccessT1190 Exploit Public-Facing Application

Rule body kusto

id: a0b9a7ca-3e6d-4996-ae35-759df1d67a54
name: OCI - Unexpected user agent
description: |
  'Detects unexpected user agent strings.'
severity: Medium
status: Available
requiredDataConnectors:
  - connectorId: OracleCloudInfrastructureLogsConnector
    dataTypes:
      - OCILogs
queryFrequency: 1h
queryPeriod: 1h
triggerOperator: gt
triggerThreshold: 0
tactics:
  - InitialAccess
relevantTechniques:
  - T1190
query: |
  OCILogs
  | where isnotempty(HttpUserAgentOriginal)
  | where strlen(HttpUserAgentOriginal) <= 10
  | extend IPCustomEntity = SrcIpAddr
entityMappings:
  - entityType: IP
    fieldMappings:
      - identifier: Address
        columnName: IPCustomEntity
version: 1.0.0
kind: Scheduled

Stages and Predicates

Stage 1: source

OCILogs

Stage 2: where

| where isnotempty(HttpUserAgentOriginal)

Stage 3: where

| where strlen(HttpUserAgentOriginal) <= 10

Stage 4: extend

| extend IPCustomEntity = SrcIpAddr

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_not_null
  • (no value, null check)
HttpUserAgentOriginalle
  • 10 transforms: strlen

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
IPCustomEntityextend