TI Map Email entity to SecurityEvent

let dt_lookBack = 1h;
let ioc_lookBack = 14d;
let emailregex = @'^[a-zA-Z0-9_.+-]+@[a-zA-Z0-9-]+\.[a-zA-Z0-9-.]+$';
ThreatIntelIndicators
//Filtering the table for Email related IOCs
| extend IndicatorType = replace(@"\[|\]|\""", "", tostring(split(ObservableKey, ":", 0)))
| where IndicatorType == "email-addr"
| extend EmailSenderAddress = ObservableValue
| extend EmailSourceDomain = substring(EmailSenderAddress, indexof(EmailSenderAddress, "@") + 1, strlen(EmailSenderAddress) - indexof(EmailSenderAddress, "@") - 1)
| extend TrafficLightProtocolLevel = tostring(parse_json(AdditionalFields).TLPLevel)
| extend IndicatorId = tostring(split(Id, "--")[2])
| extend Url = iff(ObservableKey == "url:value", ObservableValue, "")
| where TimeGenerated >= ago(ioc_lookBack)
| summarize LatestIndicatorTime = arg_max(TimeGenerated, *) by Id, ObservableValue
| where IsActive and (ValidUntil > now() or isempty(ValidUntil))
  | project-reorder *, TrafficLightProtocolLevel, EmailSenderAddress, EmailSourceDomain, Type
// 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 (
(union isfuzzy=true
(SecurityEvent
| where TimeGenerated >= ago(dt_lookBack) and isnotempty(TargetUserName)
//Normalizing the column to lower case for exact match with EmailSenderAddress column
| extend TargetUserName = tolower(TargetUserName)
// renaming timestamp column so it is clear the log this came from SecurityEvent table
| extend SecurityEvent_TimeGenerated = TimeGenerated
),
(WindowsEvent
| where TimeGenerated >= ago(dt_lookBack)
| extend TargetUserName = tostring(EventData.TargetUserName)
| where isnotempty(TargetUserName)
//Normalizing the column to lower case for exact match with EmailSenderAddress column
| extend TargetUserName = tolower(TargetUserName)
// renaming timestamp column so it is clear the log this came from SecurityEvent table
| extend SecurityEvent_TimeGenerated = TimeGenerated
))
)
on $left.EmailSenderAddress == $right.TargetUserName
| where SecurityEvent_TimeGenerated < ValidUntil
| summarize SecurityEvent_TimeGenerated = arg_max(SecurityEvent_TimeGenerated, *) by Id, TargetUserName
| extend Description = tostring(parse_json(Data).description)
| extend ActivityGroupNames = extract(@"ActivityGroup:(\S+)", 1, tostring(parse_json(Data).labels))
| project SecurityEvent_TimeGenerated, Description, ActivityGroupNames, Id, ValidUntil, Confidence,
EmailSenderAddress, Computer, EventID, TargetUserName, Activity, IpAddress, AccountType,
LogonTypeName, LogonProcessName, Status, SubStatus, Url
| extend HostName = tostring(split(Computer, '.', 0)[0]), DnsDomain = tostring(strcat_array(array_slice(split(Computer, '.'), 1, -1), '.'))
| extend timestamp = SecurityEvent_TimeGenerated

entityMappings:
- entityType: Account
  fieldMappings:
  - identifier: Name
    columnName: TargetUserName
- entityType: Host
  fieldMappings:
  - identifier: HostName
    columnName: HostName
  - identifier: DnsDomain
    columnName: DnsDomain
- entityType: IP
  fieldMappings:
  - identifier: Address
    columnName: IpAddress
- entityType: URL
  fieldMappings:
  - identifier: Url
    columnName: Url
name: TI Map Email entity to SecurityEvent
kind: Scheduled
queryFrequency: 1h
triggerOperator: gt
queryPeriod: 14d
requiredDataConnectors:
- connectorId: ThreatIntelligence
  dataTypes:
  - ThreatIntelIndicators
- connectorId: ThreatIntelligenceTaxii
  dataTypes:
  - ThreatIntelIndicators
- connectorId: SecurityEvents
  dataTypes:
  - SecurityEvent
- connectorId: WindowsSecurityEvents
  dataTypes:
  - SecurityEvents
- connectorId: WindowsForwardedEvents
  dataTypes:
  - WindowsEvent
- connectorId: MicrosoftDefenderThreatIntelligence
  dataTypes:
  - ThreatIntelIndicators
tactics:
- InitialAccess
description: |
  'Identifies a match in SecurityEvent table from any Email IOC from TI'
severity: Medium
id: 0a59051d-aed4-4fb6-bf84-bc80534482b2
triggerThreshold: 0
query: |
  let dt_lookBack = 1h;
  let ioc_lookBack = 14d;
  let emailregex = @'^[a-zA-Z0-9_.+-]+@[a-zA-Z0-9-]+\.[a-zA-Z0-9-.]+$';
  ThreatIntelIndicators
  //Filtering the table for Email related IOCs
  | extend IndicatorType = replace(@"\[|\]|\""", "", tostring(split(ObservableKey, ":", 0)))
  | where IndicatorType == "email-addr"
  | extend EmailSenderAddress = ObservableValue
  | extend EmailSourceDomain = substring(EmailSenderAddress, indexof(EmailSenderAddress, "@") + 1, strlen(EmailSenderAddress) - indexof(EmailSenderAddress, "@") - 1)
  | extend TrafficLightProtocolLevel = tostring(parse_json(AdditionalFields).TLPLevel)
  | extend IndicatorId = tostring(split(Id, "--")[2])
  | extend Url = iff(ObservableKey == "url:value", ObservableValue, "")
  | where TimeGenerated >= ago(ioc_lookBack)
  | summarize LatestIndicatorTime = arg_max(TimeGenerated, *) by Id, ObservableValue
  | where IsActive and (ValidUntil > now() or isempty(ValidUntil))
    | project-reorder *, TrafficLightProtocolLevel, EmailSenderAddress, EmailSourceDomain, Type
  // 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 (
  (union isfuzzy=true
  (SecurityEvent
  | where TimeGenerated >= ago(dt_lookBack) and isnotempty(TargetUserName)
  //Normalizing the column to lower case for exact match with EmailSenderAddress column
  | extend TargetUserName = tolower(TargetUserName)
  // renaming timestamp column so it is clear the log this came from SecurityEvent table
  | extend SecurityEvent_TimeGenerated = TimeGenerated
  ),
  (WindowsEvent
  | where TimeGenerated >= ago(dt_lookBack)
  | extend TargetUserName = tostring(EventData.TargetUserName)
  | where isnotempty(TargetUserName)
  //Normalizing the column to lower case for exact match with EmailSenderAddress column
  | extend TargetUserName = tolower(TargetUserName)
  // renaming timestamp column so it is clear the log this came from SecurityEvent table
  | extend SecurityEvent_TimeGenerated = TimeGenerated
  ))
  )
  on $left.EmailSenderAddress == $right.TargetUserName
  | where SecurityEvent_TimeGenerated < ValidUntil
  | summarize SecurityEvent_TimeGenerated = arg_max(SecurityEvent_TimeGenerated, *) by Id, TargetUserName
  | extend Description = tostring(parse_json(Data).description)
  | extend ActivityGroupNames = extract(@"ActivityGroup:(\S+)", 1, tostring(parse_json(Data).labels))
  | project SecurityEvent_TimeGenerated, Description, ActivityGroupNames, Id, ValidUntil, Confidence,
  EmailSenderAddress, Computer, EventID, TargetUserName, Activity, IpAddress, AccountType,
  LogonTypeName, LogonProcessName, Status, SubStatus, Url
  | extend HostName = tostring(split(Computer, '.', 0)[0]), DnsDomain = tostring(strcat_array(array_slice(split(Computer, '.'), 1, -1), '.'))
  | extend timestamp = SecurityEvent_TimeGenerated
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Threat%20Intelligence%20%28NEW%29/Analytic%20Rules/EmailEntity_SecurityEvent.yaml
version: 1.3.11
relevantTechniques:
- T1566

{
  "$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/0a59051d-aed4-4fb6-bf84-bc80534482b2')]",
      "kind": "Scheduled",
      "name": "[concat(parameters('workspace'),'/Microsoft.SecurityInsights/0a59051d-aed4-4fb6-bf84-bc80534482b2')]",
      "properties": {
        "alertRuleTemplateName": "0a59051d-aed4-4fb6-bf84-bc80534482b2",
        "customDetails": null,
        "description": "'Identifies a match in SecurityEvent table from any Email IOC from TI'\n",
        "displayName": "TI Map Email entity to SecurityEvent",
        "enabled": true,
        "entityMappings": [
          {
            "entityType": "Account",
            "fieldMappings": [
              {
                "columnName": "TargetUserName",
                "identifier": "Name"
              }
            ]
          },
          {
            "entityType": "Host",
            "fieldMappings": [
              {
                "columnName": "HostName",
                "identifier": "HostName"
              },
              {
                "columnName": "DnsDomain",
                "identifier": "DnsDomain"
              }
            ]
          },
          {
            "entityType": "IP",
            "fieldMappings": [
              {
                "columnName": "IpAddress",
                "identifier": "Address"
              }
            ]
          },
          {
            "entityType": "URL",
            "fieldMappings": [
              {
                "columnName": "Url",
                "identifier": "Url"
              }
            ]
          }
        ],
        "OriginalUri": "https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Threat%20Intelligence%20%28NEW%29/Analytic%20Rules/EmailEntity_SecurityEvent.yaml",
        "query": "let dt_lookBack = 1h;\nlet ioc_lookBack = 14d;\nlet emailregex = @'^[a-zA-Z0-9_.+-]+@[a-zA-Z0-9-]+\\.[a-zA-Z0-9-.]+$';\nThreatIntelIndicators\n//Filtering the table for Email related IOCs\n| extend IndicatorType = replace(@\"\\[|\\]|\\\"\"\", \"\", tostring(split(ObservableKey, \":\", 0)))\n| where IndicatorType == \"email-addr\"\n| extend EmailSenderAddress = ObservableValue\n| extend EmailSourceDomain = substring(EmailSenderAddress, indexof(EmailSenderAddress, \"@\") + 1, strlen(EmailSenderAddress) - indexof(EmailSenderAddress, \"@\") - 1)\n| extend TrafficLightProtocolLevel = tostring(parse_json(AdditionalFields).TLPLevel)\n| extend IndicatorId = tostring(split(Id, \"--\")[2])\n| extend Url = iff(ObservableKey == \"url:value\", ObservableValue, \"\")\n| where TimeGenerated >= ago(ioc_lookBack)\n| summarize LatestIndicatorTime = arg_max(TimeGenerated, *) by Id, ObservableValue\n| where IsActive and (ValidUntil > now() or isempty(ValidUntil))\n  | project-reorder *, TrafficLightProtocolLevel, EmailSenderAddress, EmailSourceDomain, Type\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(union isfuzzy=true\n(SecurityEvent\n| where TimeGenerated >= ago(dt_lookBack) and isnotempty(TargetUserName)\n//Normalizing the column to lower case for exact match with EmailSenderAddress column\n| extend TargetUserName = tolower(TargetUserName)\n// renaming timestamp column so it is clear the log this came from SecurityEvent table\n| extend SecurityEvent_TimeGenerated = TimeGenerated\n),\n(WindowsEvent\n| where TimeGenerated >= ago(dt_lookBack)\n| extend TargetUserName = tostring(EventData.TargetUserName)\n| where isnotempty(TargetUserName)\n//Normalizing the column to lower case for exact match with EmailSenderAddress column\n| extend TargetUserName = tolower(TargetUserName)\n// renaming timestamp column so it is clear the log this came from SecurityEvent table\n| extend SecurityEvent_TimeGenerated = TimeGenerated\n))\n)\non $left.EmailSenderAddress == $right.TargetUserName\n| where SecurityEvent_TimeGenerated < ValidUntil\n| summarize SecurityEvent_TimeGenerated = arg_max(SecurityEvent_TimeGenerated, *) by Id, TargetUserName\n| extend Description = tostring(parse_json(Data).description)\n| extend ActivityGroupNames = extract(@\"ActivityGroup:(\\S+)\", 1, tostring(parse_json(Data).labels))\n| project SecurityEvent_TimeGenerated, Description, ActivityGroupNames, Id, ValidUntil, Confidence,\nEmailSenderAddress, Computer, EventID, TargetUserName, Activity, IpAddress, AccountType,\nLogonTypeName, LogonProcessName, Status, SubStatus, Url\n| extend HostName = tostring(split(Computer, '.', 0)[0]), DnsDomain = tostring(strcat_array(array_slice(split(Computer, '.'), 1, -1), '.'))\n| extend timestamp = SecurityEvent_TimeGenerated\n",
        "queryFrequency": "PT1H",
        "queryPeriod": "P14D",
        "severity": "Medium",
        "subTechniques": [],
        "suppressionDuration": "PT1H",
        "suppressionEnabled": false,
        "tactics": [
          "InitialAccess"
        ],
        "techniques": [
          "T1566"
        ],
        "templateVersion": "1.3.11",
        "triggerOperator": "GreaterThan",
        "triggerThreshold": 0
      },
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules"
    }
  ]
}