TI map Email entity to Cloud App Events

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Id	0385e99c-ae45-45f4-aecf-00104485cd6b
Rulename	TI map Email entity to Cloud App Events
Description	Identifies compromises and attacks and detect malicious activities in one’s email entity from TI
Severity	Medium
Tactics	InitialAccess
Techniques	T1566
Required data connectors	MicrosoftDefenderThreatIntelligence MicrosoftThreatProtection
Kind	Scheduled
Query frequency	1h
Query period	14d
Trigger threshold	0
Trigger operator	gt
Source Uri	https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Threat Intelligence (NEW)/Analytic Rules/EmailEntity_CloudAppEvents_Updated.yaml
Version	1.0.7
Arm template	0385e99c-ae45-45f4-aecf-00104485cd6b.json

KQL

let dt_lookBack = 1h;
let ioc_lookBack = 14d;
let emailregex = @'^[a-zA-Z0-9_.+-]+@[a-zA-Z0-9-]+\.[a-zA-Z0-9-.]+$';
ThreatIntelIndicators
  | where TimeGenerated >= ago(ioc_lookBack)
  | summarize LatestIndicatorTime = arg_max(TimeGenerated, *) by Id, ObservableValue
  | where IsActive and (ValidUntil > now() or isempty(ValidUntil))
//extract key part of kv pair
  | 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)
  | project-reorder *, EmailSenderAddress, EmailSourceDomain, Type
  | extend IndicatorId = tostring(split(Id, "--")[2])
  | join kind=innerunique (CloudAppEvents
| extend User_Id = tostring(RawEventData.UserId)
| where isnotempty(User_Id)
| where TimeGenerated >= ago(dt_lookBack) and isnotempty(Application)
| extend CloudAppEvents_TimeGenerated = TimeGenerated 
| where User_Id matches regex emailregex) on $left.EmailSenderAddress == $right.User_Id
| where CloudAppEvents_TimeGenerated < ValidUntil
| summarize CloudAppEvents_TimeGenerated = argmax(CloudAppEvents_TimeGenerated, *) by IndicatorId, User_Id
| extend Name = tostring(split(User_Id, '@', 0)[0]), UPNSuffix = tostring(split(User_Id, '@', 1)[0])
| extend timestamp = CloudAppEvents_TimeGenerated

YAML

description: |
    'Identifies compromises and attacks and detect malicious activities in one's email entity from TI'
version: 1.0.7
queryFrequency: 1h
triggerThreshold: 0
tactics:
- InitialAccess
queryPeriod: 14d
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Threat Intelligence (NEW)/Analytic Rules/EmailEntity_CloudAppEvents_Updated.yaml
query: |
  let dt_lookBack = 1h;
  let ioc_lookBack = 14d;
  let emailregex = @'^[a-zA-Z0-9_.+-]+@[a-zA-Z0-9-]+\.[a-zA-Z0-9-.]+$';
  ThreatIntelIndicators
    | where TimeGenerated >= ago(ioc_lookBack)
    | summarize LatestIndicatorTime = arg_max(TimeGenerated, *) by Id, ObservableValue
    | where IsActive and (ValidUntil > now() or isempty(ValidUntil))
  //extract key part of kv pair
    | 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)
    | project-reorder *, EmailSenderAddress, EmailSourceDomain, Type
    | extend IndicatorId = tostring(split(Id, "--")[2])
    | join kind=innerunique (CloudAppEvents
  | extend User_Id = tostring(RawEventData.UserId)
  | where isnotempty(User_Id)
  | where TimeGenerated >= ago(dt_lookBack) and isnotempty(Application)
  | extend CloudAppEvents_TimeGenerated = TimeGenerated 
  | where User_Id matches regex emailregex) on $left.EmailSenderAddress == $right.User_Id
  | where CloudAppEvents_TimeGenerated < ValidUntil
  | summarize CloudAppEvents_TimeGenerated = argmax(CloudAppEvents_TimeGenerated, *) by IndicatorId, User_Id
  | extend Name = tostring(split(User_Id, '@', 0)[0]), UPNSuffix = tostring(split(User_Id, '@', 1)[0])
  | extend timestamp = CloudAppEvents_TimeGenerated  
id: 0385e99c-ae45-45f4-aecf-00104485cd6b
name: TI map Email entity to Cloud App Events
triggerOperator: gt
severity: Medium
kind: Scheduled
entityMappings:
- fieldMappings:
  - columnName: Name
    identifier: DisplayName
  - columnName: User_Id
    identifier: FullName
  - columnName: UPNSuffix
    identifier: UPNSuffix
  entityType: Account
relevantTechniques:
- T1566
requiredDataConnectors:
- dataTypes:
  - CloudAppEvents
  connectorId: MicrosoftThreatProtection
- dataTypes:
  - ThreatIntelIndicators
  connectorId: MicrosoftDefenderThreatIntelligence

ARM