AD FS Abnormal EKU object identifier attribute

// change the starttime value for a longer period of known OIDs
let starttime = 1d;
// change the lookback value for a longer period of lookback for suspicious/abnormal
let lookback = 1h;
let OIDList = SecurityEvent
| where TimeGenerated >= ago(starttime)
| where EventSourceName == 'AD FS Auditing'
| where EventID == 501
| where EventData has '/eku'
| extend OIDs = extract_all(@"<Data>([\d+\.]+)</Data>", EventData)
| mv-expand OIDs
| extend OID = tostring(OIDs)
| extend OID_Length = strlen(OID)
| project TimeGenerated, Computer, EventSourceName, EventID, OID, OID_Length, EventData
;
OIDList
| where TimeGenerated >= ago(lookback)
| join kind=leftanti (
OIDList
| where TimeGenerated between (ago(starttime) .. ago(lookback))
| summarize by OID
) on OID
| extend HostName = tostring(split(Computer, ".")[0]), DomainIndex = toint(indexof(Computer, '.'))
| extend HostNameDomain = iff(DomainIndex != -1, substring(Computer, DomainIndex + 1), Computer)

name: AD FS Abnormal EKU object identifier attribute
query: |
  // change the starttime value for a longer period of known OIDs
  let starttime = 1d;
  // change the lookback value for a longer period of lookback for suspicious/abnormal
  let lookback = 1h;
  let OIDList = SecurityEvent
  | where TimeGenerated >= ago(starttime)
  | where EventSourceName == 'AD FS Auditing'
  | where EventID == 501
  | where EventData has '/eku'
  | extend OIDs = extract_all(@"<Data>([\d+\.]+)</Data>", EventData)
  | mv-expand OIDs
  | extend OID = tostring(OIDs)
  | extend OID_Length = strlen(OID)
  | project TimeGenerated, Computer, EventSourceName, EventID, OID, OID_Length, EventData
  ;
  OIDList
  | where TimeGenerated >= ago(lookback)
  | join kind=leftanti (
  OIDList
  | where TimeGenerated between (ago(starttime) .. ago(lookback))
  | summarize by OID
  ) on OID
  | extend HostName = tostring(split(Computer, ".")[0]), DomainIndex = toint(indexof(Computer, '.'))
  | extend HostNameDomain = iff(DomainIndex != -1, substring(Computer, DomainIndex + 1), Computer)  
description: |
  'This detection uses Security events from the "AD FS Auditing" provider to detect suspicious object identifiers (OIDs) as part EventID 501 and specifically part of the Enhanced Key Usage attributes.
  This query checks to see if you have any new OIDs in the last hour that have not been seen in the previous day. New OIDs should be validated and OIDs that are very long, as indicated
  by the OID_Length field, could also be an indicator of malicious activity.
  In order to use this query you need to enable AD FS auditing on the AD FS Server.
  References:
  https://www.microsoft.com/security/blog/2022/08/24/magicweb-nobeliums-post-compromise-trick-to-authenticate-as-anyone/
  https://docs.microsoft.com/windows-server/identity/ad-fs/troubleshooting/ad-fs-tshoot-logging
  '  
tactics:
- CredentialAccess
requiredDataConnectors:
- dataTypes:
  - SecurityEvent
  connectorId: SecurityEvents
queryPeriod: 1d
queryFrequency: 1h
triggerThreshold: 0
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Detections/SecurityEvent/ADFSAbnormalEnhancedKeyUsageAttribute-OID.yaml
id: cfc1ae62-db63-4a3e-b88b-dc04030c2257
triggerOperator: gt
version: 1.0.4
relevantTechniques:
- T1552
severity: High
kind: Scheduled
metadata:
  support:
    tier: Community
  author:
    name: Microsoft Security Research
  source:
    kind: Community
  categories:
    domains:
    - Security - Others
    - Identity
entityMappings:
- entityType: Host
  fieldMappings:
  - identifier: FullName
    columnName: Computer
  - identifier: HostName
    columnName: HostName
  - identifier: DnsDomain
    columnName: HostNameDomain
tags:
- Nobelium
- MagicWeb

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "workspace": {
      "type": "String"
    }
  },
  "resources": [
    {
      "apiVersion": "2023-02-01-preview",
      "id": "[concat(resourceId('Microsoft.OperationalInsights/workspaces/providers', parameters('workspace'), 'Microsoft.SecurityInsights'),'/alertRules/cfc1ae62-db63-4a3e-b88b-dc04030c2257')]",
      "kind": "Scheduled",
      "name": "[concat(parameters('workspace'),'/Microsoft.SecurityInsights/cfc1ae62-db63-4a3e-b88b-dc04030c2257')]",
      "properties": {
        "alertRuleTemplateName": "cfc1ae62-db63-4a3e-b88b-dc04030c2257",
        "customDetails": null,
        "description": "'This detection uses Security events from the \"AD FS Auditing\" provider to detect suspicious object identifiers (OIDs) as part EventID 501 and specifically part of the Enhanced Key Usage attributes.\nThis query checks to see if you have any new OIDs in the last hour that have not been seen in the previous day. New OIDs should be validated and OIDs that are very long, as indicated\nby the OID_Length field, could also be an indicator of malicious activity.\nIn order to use this query you need to enable AD FS auditing on the AD FS Server.\nReferences:\nhttps://www.microsoft.com/security/blog/2022/08/24/magicweb-nobeliums-post-compromise-trick-to-authenticate-as-anyone/\nhttps://docs.microsoft.com/windows-server/identity/ad-fs/troubleshooting/ad-fs-tshoot-logging\n'\n",
        "displayName": "AD FS Abnormal EKU object identifier attribute",
        "enabled": true,
        "entityMappings": [
          {
            "entityType": "Host",
            "fieldMappings": [
              {
                "columnName": "Computer",
                "identifier": "FullName"
              },
              {
                "columnName": "HostName",
                "identifier": "HostName"
              },
              {
                "columnName": "HostNameDomain",
                "identifier": "DnsDomain"
              }
            ]
          }
        ],
        "OriginalUri": "https://github.com/Azure/Azure-Sentinel/blob/master/Detections/SecurityEvent/ADFSAbnormalEnhancedKeyUsageAttribute-OID.yaml",
        "query": "// change the starttime value for a longer period of known OIDs\nlet starttime = 1d;\n// change the lookback value for a longer period of lookback for suspicious/abnormal\nlet lookback = 1h;\nlet OIDList = SecurityEvent\n| where TimeGenerated >= ago(starttime)\n| where EventSourceName == 'AD FS Auditing'\n| where EventID == 501\n| where EventData has '/eku'\n| extend OIDs = extract_all(@\"<Data>([\\d+\\.]+)</Data>\", EventData)\n| mv-expand OIDs\n| extend OID = tostring(OIDs)\n| extend OID_Length = strlen(OID)\n| project TimeGenerated, Computer, EventSourceName, EventID, OID, OID_Length, EventData\n;\nOIDList\n| where TimeGenerated >= ago(lookback)\n| join kind=leftanti (\nOIDList\n| where TimeGenerated between (ago(starttime) .. ago(lookback))\n| summarize by OID\n) on OID\n| extend HostName = tostring(split(Computer, \".\")[0]), DomainIndex = toint(indexof(Computer, '.'))\n| extend HostNameDomain = iff(DomainIndex != -1, substring(Computer, DomainIndex + 1), Computer)\n",
        "queryFrequency": "PT1H",
        "queryPeriod": "P1D",
        "severity": "High",
        "suppressionDuration": "PT1H",
        "suppressionEnabled": false,
        "tactics": [
          "CredentialAccess"
        ],
        "tags": [
          "Nobelium",
          "MagicWeb"
        ],
        "techniques": [
          "T1552"
        ],
        "templateVersion": "1.0.4",
        "triggerOperator": "GreaterThan",
        "triggerThreshold": 0
      },
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules"
    }
  ]
}