Solutions/Threat Intelligence (NEW)/Analytic Rules/EmailEntity_AzureActivity.yaml

id: a9a4d1ee-0f52-4a1f-8def-a2fb4462104c
name: TI map Email entity to AzureActivity
description: |
  'Identifies a match in AzureActivity table from any Email IOC from TI'
severity: Medium
requiredDataConnectors:
  - connectorId: AzureActivity
    dataTypes:
      - AzureActivity
  - connectorId: ThreatIntelligence
    dataTypes:
      - ThreatIntelligenceIndicator
  - connectorId: ThreatIntelligenceTaxii
    dataTypes:
      - ThreatIntelligenceIndicator
  - connectorId: MicrosoftDefenderThreatIntelligence
    dataTypes:
      - ThreatIntelligenceIndicator
queryFrequency: 1h
queryPeriod: 14d
triggerOperator: gt
triggerThreshold: 0
tactics:
  - InitialAccess
relevantTechniques:
  - T1566
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 isnotempty(IndicatorType) and IndicatorType == "email-addr"
  | extend EmailSenderAddress = ObservableValue
  | extend EmailSourceDomain = substring(EmailSenderAddress, indexof(EmailSenderAddress, "@") + 1, strlen(EmailSenderAddress) - indexof(EmailSenderAddress, "@") - 1)
  | extend Url = iff(ObservableKey == "url:value", ObservableValue, "")
  | extend TrafficLightProtocolLevel = tostring(parse_json(AdditionalFields).TLPLevel)
  | where isnotempty(EmailSenderAddress)
  | where TimeGenerated >= ago(ioc_lookBack)
  | summarize LatestIndicatorTime = arg_max(TimeGenerated, *) by Id
  | where IsActive == true and ValidUntil > now()
  | project-reorder *, IsActive, 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 (
      AzureActivity | where TimeGenerated >= ago(dt_lookBack) and isnotempty(Caller)
      | extend Caller = tolower(Caller)
      | where Caller matches regex emailregex
      | extend AzureActivity_TimeGenerated = TimeGenerated
  )
  on $left.EmailSenderAddress == $right.Caller
  | where AzureActivity_TimeGenerated < ValidUntil
  | summarize AzureActivity_TimeGenerated = arg_max(AzureActivity_TimeGenerated, *) by Id, Caller
  | extend Description = tostring(parse_json(Data).description)
  | extend ActivityGroupNames = extract(@"ActivityGroup:(\S+)", 1, tostring(parse_json(Data).labels))
  | project AzureActivity_TimeGenerated, Description, ActivityGroupNames, Id, ValidUntil, Confidence, EmailSenderAddress, EmailSourceDomain, Caller, CallerIpAddress, Url
  | extend Name = tostring(split(Caller, '@', 0)[0]), UPNSuffix = tostring(split(Caller, '@', 1)[0])
  | extend timestamp = AzureActivity_TimeGenerated
entityMappings:
  - entityType: Account
    fieldMappings:
      - identifier: FullName
        columnName: Caller
      - identifier: Name
        columnName: Name
      - identifier: UPNSuffix
        columnName: UPNSuffix
  - entityType: IP
    fieldMappings:
      - identifier: Address
        columnName: CallerIpAddress
  - entityType: URL
    fieldMappings:
      - identifier: Url
        columnName: Url
version: 1.2.9
kind: Scheduled