TI map Email entity to SecurityAlert

let dt_lookBack = 1h;
let ioc_lookBack = 14d;
let emailregex = @'^[a-zA-Z0-9_.+-]+@[a-zA-Z0-9-]+\.[a-zA-Z0-9-.]+$';
ThreatIntelligenceIndicator
//Filtering the table for Email related IOCs
| where isnotempty(EmailSenderAddress)
| where TimeGenerated >= ago(ioc_lookBack)
| summarize LatestIndicatorTime = arg_max(TimeGenerated, *) by IndicatorId
| where Active == true and ExpirationDateTime > now()
// using innerunique to keep perf fast and result set low, we only need one match to indicate potential malicious activity that needs to be investigated
| join kind=innerunique (
    SecurityAlert
    | where TimeGenerated >= ago(dt_lookBack)
    | extend MSTI = case(AlertName has "TI map" and VendorName == "Microsoft" and ProductName == 'Azure Sentinel', true, false)
    | where MSTI == false
    // Converting Entities into dynamic data type and use mv-expand to unpack the array
    | extend EntitiesDynamicArray = parse_json(Entities) | mv-expand EntitiesDynamicArray
    // Parsing relevant entity column to filter type account and creating new column by combining account and UPNSuffix
    | extend Entitytype = tostring(parse_json(EntitiesDynamicArray).Type), EntityName = tostring(parse_json(EntitiesDynamicArray).Name),
    EntityUPNSuffix = tostring(parse_json(EntitiesDynamicArray).UPNSuffix)
    | where Entitytype =~ "account"
    | extend EntityEmail = tolower(strcat(EntityName, "@", EntityUPNSuffix))
    | where EntityEmail matches regex emailregex
    | extend Alert_TimeGenerated = TimeGenerated
)
on $left.EmailSenderAddress == $right.EntityEmail
| where Alert_TimeGenerated < ExpirationDateTime
| summarize Alert_TimeGenerated = arg_max(Alert_TimeGenerated, *) by IndicatorId, AlertName
| project Alert_TimeGenerated, Description, ActivityGroupNames, IndicatorId, ThreatType, Url, ExpirationDateTime, ConfidenceScore,
EmailSenderName, EmailRecipient, EmailSourceDomain, EmailSourceIpAddress, EmailSubject, FileHashValue, FileHashType, EntityEmail, AlertName, AlertType,
AlertSeverity, Entities, ProviderName, VendorName
| extend Name = tostring(split(EntityEmail, '@', 0)[0]), UPNSuffix = tostring(split(EntityEmail, '@', 1)[0])
| extend timestamp = Alert_TimeGenerated

relevantTechniques:
- T1566
name: TI map Email entity to SecurityAlert
requiredDataConnectors:
- dataTypes:
  - SecurityAlert
  connectorId: AzureSecurityCenter
- dataTypes:
  - ThreatIntelligenceIndicator
  connectorId: ThreatIntelligence
- dataTypes:
  - ThreatIntelligenceIndicator
  connectorId: ThreatIntelligenceTaxii
- dataTypes:
  - ThreatIntelligenceIndicator
  connectorId: MicrosoftDefenderThreatIntelligence
entityMappings:
- fieldMappings:
  - identifier: FullName
    columnName: EntityEmail
  - identifier: Name
    columnName: Name
  - identifier: UPNSuffix
    columnName: UPNSuffix
  entityType: Account
- fieldMappings:
  - identifier: Url
    columnName: Url
  entityType: URL
triggerThreshold: 0
id: a2e36ce0-da4d-4b6e-88c6-4e40161c5bfc
tactics:
- InitialAccess
version: 1.2.8
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Threat Intelligence/Analytic Rules/EmailEntity_SecurityAlert.yaml
queryPeriod: 14d
kind: Scheduled
queryFrequency: 1h
severity: Medium
description: |
    'Identifies a match in SecurityAlert table from any Email IOC from TI which will extend coverage to datatypes such as MCAS, StorageThreatProtection and many others'
query: |
  let dt_lookBack = 1h;
  let ioc_lookBack = 14d;
  let emailregex = @'^[a-zA-Z0-9_.+-]+@[a-zA-Z0-9-]+\.[a-zA-Z0-9-.]+$';
  ThreatIntelligenceIndicator
  //Filtering the table for Email related IOCs
  | where isnotempty(EmailSenderAddress)
  | where TimeGenerated >= ago(ioc_lookBack)
  | summarize LatestIndicatorTime = arg_max(TimeGenerated, *) by IndicatorId
  | where Active == true and ExpirationDateTime > now()
  // using innerunique to keep perf fast and result set low, we only need one match to indicate potential malicious activity that needs to be investigated
  | join kind=innerunique (
      SecurityAlert
      | where TimeGenerated >= ago(dt_lookBack)
      | extend MSTI = case(AlertName has "TI map" and VendorName == "Microsoft" and ProductName == 'Azure Sentinel', true, false)
      | where MSTI == false
      // Converting Entities into dynamic data type and use mv-expand to unpack the array
      | extend EntitiesDynamicArray = parse_json(Entities) | mv-expand EntitiesDynamicArray
      // Parsing relevant entity column to filter type account and creating new column by combining account and UPNSuffix
      | extend Entitytype = tostring(parse_json(EntitiesDynamicArray).Type), EntityName = tostring(parse_json(EntitiesDynamicArray).Name),
      EntityUPNSuffix = tostring(parse_json(EntitiesDynamicArray).UPNSuffix)
      | where Entitytype =~ "account"
      | extend EntityEmail = tolower(strcat(EntityName, "@", EntityUPNSuffix))
      | where EntityEmail matches regex emailregex
      | extend Alert_TimeGenerated = TimeGenerated
  )
  on $left.EmailSenderAddress == $right.EntityEmail
  | where Alert_TimeGenerated < ExpirationDateTime
  | summarize Alert_TimeGenerated = arg_max(Alert_TimeGenerated, *) by IndicatorId, AlertName
  | project Alert_TimeGenerated, Description, ActivityGroupNames, IndicatorId, ThreatType, Url, ExpirationDateTime, ConfidenceScore,
  EmailSenderName, EmailRecipient, EmailSourceDomain, EmailSourceIpAddress, EmailSubject, FileHashValue, FileHashType, EntityEmail, AlertName, AlertType,
  AlertSeverity, Entities, ProviderName, VendorName
  | extend Name = tostring(split(EntityEmail, '@', 0)[0]), UPNSuffix = tostring(split(EntityEmail, '@', 1)[0])
  | extend timestamp = Alert_TimeGenerated  
triggerOperator: gt

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "workspace": {
      "type": "String"
    }
  },
  "resources": [
    {
      "apiVersion": "2024-01-01-preview",
      "id": "[concat(resourceId('Microsoft.OperationalInsights/workspaces/providers', parameters('workspace'), 'Microsoft.SecurityInsights'),'/alertRules/a2e36ce0-da4d-4b6e-88c6-4e40161c5bfc')]",
      "kind": "Scheduled",
      "name": "[concat(parameters('workspace'),'/Microsoft.SecurityInsights/a2e36ce0-da4d-4b6e-88c6-4e40161c5bfc')]",
      "properties": {
        "alertRuleTemplateName": "a2e36ce0-da4d-4b6e-88c6-4e40161c5bfc",
        "customDetails": null,
        "description": "'Identifies a match in SecurityAlert table from any Email IOC from TI which will extend coverage to datatypes such as MCAS, StorageThreatProtection and many others'\n",
        "displayName": "TI map Email entity to SecurityAlert",
        "enabled": true,
        "entityMappings": [
          {
            "entityType": "Account",
            "fieldMappings": [
              {
                "columnName": "EntityEmail",
                "identifier": "FullName"
              },
              {
                "columnName": "Name",
                "identifier": "Name"
              },
              {
                "columnName": "UPNSuffix",
                "identifier": "UPNSuffix"
              }
            ]
          },
          {
            "entityType": "URL",
            "fieldMappings": [
              {
                "columnName": "Url",
                "identifier": "Url"
              }
            ]
          }
        ],
        "OriginalUri": "https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Threat Intelligence/Analytic Rules/EmailEntity_SecurityAlert.yaml",
        "query": "let dt_lookBack = 1h;\nlet ioc_lookBack = 14d;\nlet emailregex = @'^[a-zA-Z0-9_.+-]+@[a-zA-Z0-9-]+\\.[a-zA-Z0-9-.]+$';\nThreatIntelligenceIndicator\n//Filtering the table for Email related IOCs\n| where isnotempty(EmailSenderAddress)\n| where TimeGenerated >= ago(ioc_lookBack)\n| summarize LatestIndicatorTime = arg_max(TimeGenerated, *) by IndicatorId\n| where Active == true and ExpirationDateTime > now()\n// using innerunique to keep perf fast and result set low, we only need one match to indicate potential malicious activity that needs to be investigated\n| join kind=innerunique (\n    SecurityAlert\n    | where TimeGenerated >= ago(dt_lookBack)\n    | extend MSTI = case(AlertName has \"TI map\" and VendorName == \"Microsoft\" and ProductName == 'Azure Sentinel', true, false)\n    | where MSTI == false\n    // Converting Entities into dynamic data type and use mv-expand to unpack the array\n    | extend EntitiesDynamicArray = parse_json(Entities) | mv-expand EntitiesDynamicArray\n    // Parsing relevant entity column to filter type account and creating new column by combining account and UPNSuffix\n    | extend Entitytype = tostring(parse_json(EntitiesDynamicArray).Type), EntityName = tostring(parse_json(EntitiesDynamicArray).Name),\n    EntityUPNSuffix = tostring(parse_json(EntitiesDynamicArray).UPNSuffix)\n    | where Entitytype =~ \"account\"\n    | extend EntityEmail = tolower(strcat(EntityName, \"@\", EntityUPNSuffix))\n    | where EntityEmail matches regex emailregex\n    | extend Alert_TimeGenerated = TimeGenerated\n)\non $left.EmailSenderAddress == $right.EntityEmail\n| where Alert_TimeGenerated < ExpirationDateTime\n| summarize Alert_TimeGenerated = arg_max(Alert_TimeGenerated, *) by IndicatorId, AlertName\n| project Alert_TimeGenerated, Description, ActivityGroupNames, IndicatorId, ThreatType, Url, ExpirationDateTime, ConfidenceScore,\nEmailSenderName, EmailRecipient, EmailSourceDomain, EmailSourceIpAddress, EmailSubject, FileHashValue, FileHashType, EntityEmail, AlertName, AlertType,\nAlertSeverity, Entities, ProviderName, VendorName\n| extend Name = tostring(split(EntityEmail, '@', 0)[0]), UPNSuffix = tostring(split(EntityEmail, '@', 1)[0])\n| extend timestamp = Alert_TimeGenerated\n",
        "queryFrequency": "PT1H",
        "queryPeriod": "P14D",
        "severity": "Medium",
        "subTechniques": [],
        "suppressionDuration": "PT1H",
        "suppressionEnabled": false,
        "tactics": [
          "InitialAccess"
        ],
        "techniques": [
          "T1566"
        ],
        "templateVersion": "1.2.8",
        "triggerOperator": "GreaterThan",
        "triggerThreshold": 0
      },
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules"
    }
  ]
}