Detection rules › Kusto

TI map Email entity to SigninLogs

Severity
medium
Time window
14d
Group by
EmailSenderAddress, IndicatorId, UserPrincipalName
Source
github.com/Azure/Azure-Sentinel

'Identifies a match in SigninLogs table from any Email IOC from TI'

MITRE ATT&CK coverage

TacticTechniques
Initial AccessT1566 Phishing

Rule body kusto

id: 30fa312c-31eb-43d8-b0cc-bcbdfb360822
name: TI map Email entity to SigninLogs
description: |
  'Identifies a match in SigninLogs table from any Email IOC from TI'
severity: Medium
requiredDataConnectors:
  - connectorId: ThreatIntelligence
    dataTypes:
      - ThreatIntelligenceIndicator
  - connectorId: ThreatIntelligenceTaxii
    dataTypes:
      - ThreatIntelligenceIndicator
  - connectorId: AzureActiveDirectory
    dataTypes:
      - SigninLogs
  - connectorId: AzureActiveDirectory
    dataTypes:
      - AADNonInteractiveUserSignInLogs
  - 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-.]+$';
  let Signins = materialize(union isfuzzy=true
  ( SigninLogs | where TimeGenerated >= ago(dt_lookBack)),
  ( AADNonInteractiveUserSignInLogs | where TimeGenerated >= ago(dt_lookBack)
      | extend Status = todynamic(Status), LocationDetails = todynamic(LocationDetails))
  | where isnotempty(UserPrincipalName) and UserPrincipalName matches regex emailregex
  | extend UserPrincipalName = tolower(UserPrincipalName)
  | extend Status = todynamic(Status), LocationDetails = todynamic(LocationDetails)
  | extend StatusCode = tostring(Status.errorCode), StatusDetails = tostring(Status.additionalDetails)
  | extend State = tostring(LocationDetails.state), City = tostring(LocationDetails.city), Region = tostring(LocationDetails.countryOrRegion)
  | extend SigninLogs_TimeGenerated = TimeGenerated);
  let SigninUPNs = Signins | distinct UserPrincipalName | summarize make_list(UserPrincipalName);
  ThreatIntelligenceIndicator
  //Filtering the table for Email related IOCs
  | where isnotempty(EmailSenderAddress)
  | where TimeGenerated >= ago(ioc_lookBack)
  | where EmailSenderAddress in (SigninUPNs)
  | summarize LatestIndicatorTime = arg_max(TimeGenerated, *) by IndicatorId
  | where Active == true and ExpirationDateTime > now()
  | where Description !contains_cs "State: inactive;" and Description !contains_cs "State: falsepos;"
  | join kind=innerunique (Signins) on $left.EmailSenderAddress == $right.UserPrincipalName
  | where SigninLogs_TimeGenerated < ExpirationDateTime
  | summarize SigninLogs_TimeGenerated = arg_max(SigninLogs_TimeGenerated, *) by IndicatorId, UserPrincipalName
  | project SigninLogs_TimeGenerated, Description, ActivityGroupNames, IndicatorId, ThreatType, Url, ExpirationDateTime, ConfidenceScore, EmailSenderName, EmailRecipient, EmailSourceDomain, EmailSourceIpAddress, EmailSubject, FileHashValue, FileHashType, IPAddress, UserPrincipalName, AppDisplayName, StatusCode, StatusDetails, NetworkIP, NetworkDestinationIP, NetworkSourceIP, Type
  | extend Name = tostring(split(UserPrincipalName, '@', 0)[0]), UPNSuffix = tostring(split(UserPrincipalName, '@', 1)[0])
  | extend timestamp = SigninLogs_TimeGenerated
entityMappings:
  - entityType: Account
    fieldMappings:
      - identifier: FullName
        columnName: UserPrincipalName
      - identifier: Name
        columnName: Name
      - identifier: UPNSuffix
        columnName: UPNSuffix 
  - entityType: IP
    fieldMappings:
      - identifier: Address
        columnName: IPAddress
  - entityType: URL
    fieldMappings:
      - identifier: Url
        columnName: Url
version: 1.2.7
kind: Scheduled

Stages and Predicates

Parameters

let dt_lookBack = 1h;
let ioc_lookBack = 14d;
let emailregex = @'^[a-zA-Z0-9_.+-]+@[a-zA-Z0-9-]+\.[a-zA-Z0-9-.]+$';

Let binding: Signins

let Signins = materialize(union isfuzzy=true
( SigninLogs | where TimeGenerated >= ago(dt_lookBack)),
( AADNonInteractiveUserSignInLogs | where TimeGenerated >= ago(dt_lookBack)
    | extend Status = todynamic(Status), LocationDetails = todynamic(LocationDetails))
| where isnotempty(UserPrincipalName) and UserPrincipalName matches regex emailregex
| extend UserPrincipalName = tolower(UserPrincipalName)
| extend Status = todynamic(Status), LocationDetails = todynamic(LocationDetails)
| extend StatusCode = tostring(Status.errorCode), StatusDetails = tostring(Status.additionalDetails)
| extend State = tostring(LocationDetails.state), City = tostring(LocationDetails.city), Region = tostring(LocationDetails.countryOrRegion)
| extend SigninLogs_TimeGenerated = TimeGenerated);

Derived from dt_lookBack, emailregex.

Let binding: SigninUPNs

let SigninUPNs = Signins | distinct UserPrincipalName | summarize make_list(UserPrincipalName);

Derived from Signins.

Stage 1: source

ThreatIntelligenceIndicator

Stage 2: where

| where isnotempty(EmailSenderAddress)

Stage 3: where

| where TimeGenerated >= ago(ioc_lookBack)

Stage 4: where

| where EmailSenderAddress in (SigninUPNs)

References SigninUPNs (defined above).

Stage 5: summarize

| summarize LatestIndicatorTime = arg_max(TimeGenerated, *) by IndicatorId

Stage 6: where

| where Active == true and ExpirationDateTime > now()

Stage 7: where

| where Description !contains_cs "State: inactive;" and Description !contains_cs "State: falsepos;"

Stage 8: join

| join kind=innerunique (Signins) on $left.EmailSenderAddress == $right.UserPrincipalName

Stage 9: where

| where SigninLogs_TimeGenerated < ExpirationDateTime

Stage 10: summarize

| summarize SigninLogs_TimeGenerated = arg_max(SigninLogs_TimeGenerated, *) by IndicatorId, UserPrincipalName

Stage 11: project

| project SigninLogs_TimeGenerated, Description, ActivityGroupNames, IndicatorId, ThreatType, Url, ExpirationDateTime, ConfidenceScore, EmailSenderName, EmailRecipient, EmailSourceDomain, EmailSourceIpAddress, EmailSubject, FileHashValue, FileHashType, IPAddress, UserPrincipalName, AppDisplayName, StatusCode, StatusDetails, NetworkIP, NetworkDestinationIP, NetworkSourceIP, Type

Stage 12: extend

| extend Name = tostring(split(UserPrincipalName, '@', 0)[0]), UPNSuffix = tostring(split(UserPrincipalName, '@', 1)[0])

Stage 13: extend

| extend timestamp = SigninLogs_TimeGenerated

Exclusions

Top-level NOT(...) conjuncts: predicates this rule actively suppresses.

FieldKindExcluded values
DescriptioncontainsState: falsepos;
DescriptioncontainsState: inactive;

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

FieldKindValues
Activeeq
  • true transforms: cased
EmailSenderAddressin
  • SigninUPNs transforms: cased
EmailSenderAddressis_not_null
  • (no value, null check)
SigninLogs_TimeGeneratedlt
  • ExpirationDateTime transforms: cased
UserPrincipalNameis_not_null
  • (no value, null check)
UserPrincipalNameregex_match
  • ^[a-zA-Z0-9_.+-]+@[a-zA-Z0-9-]+.[a-zA-Z0-9-.]+$

Output fields

Fields the rule emits when it matches. Chronicle authors list these in the outcome block; they appear on the detection and $risk_score drives alerting. Sentinel / Defender XDR rules build them up through project / summarize / extend stages. Sentinel maps these into alert fields via entityMappings and customDetails; Defender XDR custom detections surface them as alert fields directly.

FieldSource
ActivityGroupNamesproject
AppDisplayNameproject
ConfidenceScoreproject
Descriptionproject
EmailRecipientproject
EmailSenderNameproject
EmailSourceDomainproject
EmailSourceIpAddressproject
EmailSubjectproject
ExpirationDateTimeproject
FileHashTypeproject
FileHashValueproject
IPAddressproject
IndicatorIdproject
NetworkDestinationIPproject
NetworkIPproject
NetworkSourceIPproject
SigninLogs_TimeGeneratedproject
StatusCodeproject
StatusDetailsproject
ThreatTypeproject
Typeproject
Urlproject
UserPrincipalNameproject
Nameextend
UPNSuffixextend
timestampextend