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Detection rules › Kusto

Tenable.ad user accounts issues

Severity
low
Time window
2h
Source
github.com/Azure/Azure-Sentinel

'Searches for triggered Indicators of Exposures related to user accounts issues.'

MITRE ATT&CK coverage

TacticTechniques
Credential AccessT1110 Brute Force

Rule body kusto

id: 4f8ed6f3-8815-437d-9462-f0def9dc70d6
name: Tenable.ad user accounts issues
description: |
    'Searches for triggered Indicators of Exposures related to user accounts issues.'
severity: Low
requiredDataConnectors:
  - connectorId: Tenable.ad
    dataTypes:
      - Tenable_ad_CL
queryFrequency: 2h
queryPeriod: 2h
triggerOperator: gt
triggerThreshold: 0
tactics:
  - CredentialAccess
relevantTechniques:
  - T1110
query: |
  // For the query to work properly, make sure you have imported the afad_parser.kql parser into the workspace
  // Retrieve the parser here: https://raw.githubusercontent.com/tenable/Azure-Sentinel/Tenable.ad-connector/Solutions/TenableAD/Parsers/afad_parser.kql
  // Then, create the Kusto Function with alias afad_parser
  let SeverityTable=datatable(Severity:string,Level:int) [
  "low", 1,
  "medium", 2,
  "high", 3,
  "critical", 4
  ];
  let codeNameList = datatable(Codename:string)["C-ACCOUNTS-DANG-SID-HISTORY", "C-PRE-WIN2000-ACCESS-MEMBERS", "C-PASSWORD-DONT-EXPIRE", "C-SLEEPING-ACCOUNTS", "C-DANG-PRIMGROUPID", "C-PASSWORD-NOT-REQUIRED", "C-USER-PASSWORD"];
  afad_parser
  | where MessageType == 0 and Codename in~ (codeNameList)
  | lookup kind=leftouter SeverityTable on Severity
  | order by Level
  | extend HostName = tostring(split(Host, '.', 0)[0]), DnsDomain = tostring(strcat_array(array_slice(split(Host, '.'), 1, -1), '.'))
entityMappings:
  - entityType: Host
    fieldMappings:
      - identifier: HostName
        columnName: HostName
      - identifier: DnsDomain
        columnName: DnsDomain
version: 1.0.1
kind: Scheduled

Stages and Predicates

Let binding: SeverityTable

let SeverityTable = datatable(Severity:string,Level:int) [
"low", 1,
"medium", 2,
"high", 3,
"critical", 4
];

Let binding: codeNameList

let codeNameList = datatable(Codename:string)["C-ACCOUNTS-DANG-SID-HISTORY", "C-PRE-WIN2000-ACCESS-MEMBERS", "C-PASSWORD-DONT-EXPIRE", "C-SLEEPING-ACCOUNTS", "C-DANG-PRIMGROUPID", "C-PASSWORD-NOT-REQUIRED", "C-USER-PASSWORD"];

Stage 1: source

afad_parser

Stage 2: where

| where MessageType == 0 and Codename in~ (codeNameList)

References codeNameList (defined above).

Stage 3: kusto:lookup

| lookup kind=leftouter SeverityTable on Severity

Stage 4: sort

| order by Level

Stage 5: extend

| extend HostName = tostring(split(Host, '.', 0)[0]), DnsDomain = tostring(strcat_array(array_slice(split(Host, '.'), 1, -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
Codenamein
  • codeNameList corpus 12 (kusto 12)
MessageTypeeq
  • 0 transforms: cased corpus 15 (kusto 15)

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
DnsDomainextend
HostNameextend