TI Map Email entity to EmailEvents

Severity: medium
Time window: 14d
Group by: Id, ObservableValue, RecipientEmailAddress, SenderFromAddress, TI_EmailAddress
Source: github.com/Azure/Azure-Sentinel

Identifies a match in EmailEvents table from any Email IOC from TI

MITRE ATT&CK coverage

Tactic	Techniques
Initial Access	`T1566` Phishing

Telemetry coverage

Platform	Record / event type
Microsoft Defender for Endpoint	`EmailEvents` action `any`: Email processed

Rule body

id: 18b61c3f-55fa-4eb9-8721-72dabd1eb3cb
name: TI Map Email entity to EmailEvents
description: |
  'Identifies a match in EmailEvents table from any Email IOC from TI'
severity: Medium
requiredDataConnectors:
  - connectorId: MicrosoftThreatProtection
    dataTypes:
      - EmailEvents
  - connectorId: ThreatIntelligence
    dataTypes:
      - ThreatIntelIndicators
  - connectorId: ThreatIntelligenceTaxii
    dataTypes:
      - ThreatIntelIndicators
  - connectorId: MicrosoftDefenderThreatIntelligence
    dataTypes:
      - ThreatIntelIndicators
queryFrequency: 1h
queryPeriod: 14d
triggerOperator: gt
triggerThreshold: 0
tactics:
  - InitialAccess
relevantTechniques:
  - T1566
query: |
  let dt_lookBack = 1h;
  let ioc_lookBack = 14d;
  let EmailEvents_ = materialize(EmailEvents | where isnotempty(RecipientEmailAddress) and isnotempty(SenderFromAddress) and TimeGenerated >= ago(dt_lookBack) and DeliveryAction !has "Blocked" | project-rename  EmailEvents_TimeGenerated = TimeGenerated | extend SenderFromAddress = tolower(SenderFromAddress) | extend RecipientEmailAddress = tolower(RecipientEmailAddress));
  let SenderAddresses = EmailEvents_ | distinct  SenderFromAddress | summarize make_list(SenderFromAddress);
  let RecipientAddresses = EmailEvents_ | distinct  RecipientEmailAddress | summarize make_list(RecipientEmailAddress);
  let TI = materialize(ThreatIntelIndicators
  | where TimeGenerated >= ago(ioc_lookBack)
  | 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 TI_EmailAddress = tolower(EmailSenderAddress)
  | where TI_EmailAddress in (SenderAddresses) or TI_EmailAddress in (RecipientAddresses)
  | summarize LatestIndicatorTime = arg_max(TimeGenerated, *) by Id, ObservableValue
  | where IsActive and (ValidUntil > now() or isempty(ValidUntil)));
  (union
    (TI | join kind=innerunique (EmailEvents_) on $left.TI_EmailAddress == $right.SenderFromAddress),
    (TI | join kind=innerunique (EmailEvents_) on $left.TI_EmailAddress == $right.RecipientEmailAddress))
  | where EmailEvents_TimeGenerated < ValidUntil
  | extend Description = tostring(parse_json(Data).description)
  | extend ActivityGroupNames = extract("ActivityGroup:([^,]+)", 1, tostring(parse_json(Data).labels))
  | summarize EmailEvents_TimeGenerated = arg_max(EmailEvents_TimeGenerated, *) by Id, TI_EmailAddress
  | extend DomainName = EmailSourceDomain
  | extend Url = DomainName
  | project EmailEvents_TimeGenerated, Description, ActivityGroupNames, Id, ValidUntil, Confidence, DomainName, RecipientEmailAddress, SenderFromAddress, Subject, ConfidenceLevel, Url, Type, TI_EmailAddress, TrafficLightProtocolLevel, DeliveryAction, DeliveryLocation, EmailDirection
  | extend Name = tostring(split(RecipientEmailAddress, '@', 0)[0]), UPNSuffix = tostring(split(RecipientEmailAddress, '@', 1)[0])
  | extend timestamp = EmailEvents_TimeGenerated
  | project-reorder *, TrafficLightProtocolLevel, DomainName, Type, TI_EmailAddress
entityMappings:
  - entityType: Account
    fieldMappings:
      - identifier: FullName
        columnName: RecipientEmailAddress
      - identifier: Name
        columnName: Name
      - identifier: UPNSuffix
        columnName: UPNSuffix
version: 1.0.6
kind: Scheduled

Stages and Predicates

Stage 0: `let`

let dt_lookBack = 1h;
let ioc_lookBack = 14d;
let EmailEvents_ = materialize(EmailEvents | where isnotempty(RecipientEmailAddress) and isnotempty(SenderFromAddress) and TimeGenerated >= ago(dt_lookBack) and DeliveryAction !has "Blocked" | project-rename  EmailEvents_TimeGenerated = TimeGenerated | extend SenderFromAddress = tolower(SenderFromAddress) | extend RecipientEmailAddress = tolower(RecipientEmailAddress));
let SenderAddresses = EmailEvents_ | distinct  SenderFromAddress | summarize make_list(SenderFromAddress);
let RecipientAddresses = EmailEvents_ | distinct  RecipientEmailAddress | summarize make_list(RecipientEmailAddress);
let TI = materialize(<inlined as stages below>);

Stage 1: `source`

let EmailEvents_

Stage 2: `source`

let SenderAddresses

Stage 3: `source`

let RecipientAddresses

Stage 4: `union`

union of 2 branches

Stage 5: `source`

ThreatIntelIndicators

Stage 6: `where`

where TimeGenerated >= ago(1209600s)

Stage 7: `extend`

extend IndicatorType

Stage 8: `where`

where IndicatorType =~ "email-addr"

Stage 9: `extend` (4 consecutive steps)

extend EmailSenderAddress, EmailSourceDomain, TI_EmailAddress, TrafficLightProtocolLevel

Stage 10: `where`

where (TI_EmailAddress =~ "RecipientAddresses" or TI_EmailAddress =~ "SenderAddresses")

Stage 11: `summarize`

summarize LatestIndicatorTime by Id, ObservableValue

Stage 12: `where`

where (isempty(ValidUntil) or ValidUntil > now())

Stage 13: `join`

join kind=innerunique (EmailEvents_) on TI_EmailAddress, SenderFromAddress

Stage 14: `source`

ThreatIntelIndicators

Stage 15: `where`

where TimeGenerated >= ago(1209600s)

Stage 16: `extend`

extend IndicatorType

Stage 17: `where`

where IndicatorType =~ "email-addr"

Stage 18: `extend` (4 consecutive steps)

extend EmailSenderAddress, EmailSourceDomain, TI_EmailAddress, TrafficLightProtocolLevel

Stage 19: `where`

where (TI_EmailAddress =~ "RecipientAddresses" or TI_EmailAddress =~ "SenderAddresses")

Stage 20: `summarize`

summarize LatestIndicatorTime by Id, ObservableValue

Stage 21: `where`

where (isempty(ValidUntil) or ValidUntil > now())

Stage 22: `join`

join kind=innerunique (EmailEvents_) on TI_EmailAddress, RecipientEmailAddress

Stage 23: `where`

where EmailEvents_TimeGenerated < ValidUntil

Stage 24: `extend`

extend Description

Stage 25: `extend`

extend ActivityGroupNames

Stage 26: `summarize`

summarize EmailEvents_TimeGenerated by Id, TI_EmailAddress

Stage 27: `extend`

extend DomainName

Stage 28: `extend`

extend Url

Stage 29: `project`

project ActivityGroupNames, Confidence, ConfidenceLevel, DeliveryAction, DeliveryLocation, Description, DomainName, EmailDirection, EmailEvents_TimeGenerated, Id, RecipientEmailAddress, SenderFromAddress, Subject, TI_EmailAddress, TrafficLightProtocolLevel, Type, Url, ValidUntil

Stage 30: `extend`

extend Name, UPNSuffix

Stage 31: `extend`

extend timestamp

Stage 32: `project-reorder`

project-reorder

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`EmailEvents_TimeGenerated`	cross_field_compare	`ValidUntil` transforms: `op:lt`	`field:"EmailEvents_TimeGenerated" kind:cross_field_compare value:"ValidUntil"`
`IndicatorType`	eq	`email-addr`	`field:"IndicatorType" kind:eq value:"email-addr"`
`RecipientEmailAddress`	is_not_null	(no value, null check)	`field:"RecipientEmailAddress" kind:is_not_null`
`SenderFromAddress`	is_not_null	(no value, null check)	`field:"SenderFromAddress" kind:is_not_null`
`TI_EmailAddress`	in	`RecipientAddresses` `SenderAddresses`	`field:"TI_EmailAddress" kind:in`
`ValidUntil`	is_null	(no value, null check)	`field:"ValidUntil" kind:is_null`

Exclusions

The rule actively suppresses these predicates.

Field	Kind	Excluded values	Search
`DeliveryAction`	match	`Blocked`	`excludes:DeliveryAction` `field:"DeliveryAction" value:"Blocked"`

Output fields

These fields are emitted when the rule matches.

Field	Source
`ActivityGroupNames`	`project`
`Confidence`	`project`
`ConfidenceLevel`	`project`
`DeliveryAction`	`project`
`DeliveryLocation`	`project`
`Description`	`project`
`DomainName`	`project`
`EmailDirection`	`project`
`EmailEvents_TimeGenerated`	`project`
`Id`	`project`
`RecipientEmailAddress`	`project`
`SenderFromAddress`	`project`
`Subject`	`project`
`TI_EmailAddress`	`project`
`TrafficLightProtocolLevel`	`project`
`Type`	`project`
`Url`	`project`
`ValidUntil`	`project`
`Name`	`extend`
`UPNSuffix`	`extend`
`timestamp`	`extend`

TI Map Email entity to EmailEvents

MITRE ATT&CK coverage

Telemetry coverage

Rule body

Stages and Predicates

Stage 0: let

Stage 1: source

Stage 2: source

Stage 3: source

Stage 4: union

Stage 5: source

Stage 6: where

Stage 7: extend

Stage 8: where

Stage 9: extend (4 consecutive steps)

Stage 10: where

Stage 11: summarize

Stage 12: where

Stage 13: join

Stage 14: source

Stage 15: where

Stage 16: extend

Stage 17: where

Stage 18: extend (4 consecutive steps)

Stage 19: where

Stage 20: summarize

Stage 21: where

Stage 22: join

Stage 23: where

Stage 24: extend

Stage 25: extend

Stage 26: summarize

Stage 27: extend

Stage 28: extend

Stage 29: project

Stage 30: extend

Stage 31: extend

Stage 32: project-reorder