Rare application consent

id: 83ba3057-9ea3-4759-bf6a-933f2e5bc7ee
name: Rare application consent
description: |
  'This will alert when the "Consent to application" operation occurs by a user that has not done this operation before or rarely does this.
  This could indicate that permissions to access the listed Azure App were provided to a malicious actor.
  Consent to application, Add service principal and Add OAuth2PermissionGrant should typically be rare events.
  This may help detect the Oauth2 attack that can be initiated by this publicly available tool - https://github.com/fireeye/PwnAuth
  For further information on AuditLogs please see https://docs.microsoft.com/azure/active-directory/reports-monitoring/reference-audit-activities.'
severity: Medium
status: Available
requiredDataConnectors:
  - connectorId: AzureActiveDirectory
    dataTypes:
      - AuditLogs
queryFrequency: 1d
queryPeriod: 7d
triggerOperator: gt
triggerThreshold: 3
tactics:
  - Persistence
  - PrivilegeEscalation
relevantTechniques:
  - T1136
  - T1068
query: |
  let current = 1d;
  let auditLookback = 7d;
  // Setting threshold to 3 as a default, change as needed.
  // Any operation that has been initiated by a user or app more than 3 times in the past 7 days will be excluded
  let threshold = 3;
  // Gather initial data from lookback period, excluding current, adjust current to more than a single day if no results
  let AuditTrail = AuditLogs | where TimeGenerated >= ago(auditLookback) and TimeGenerated < ago(current)
  // 2 other operations that can be part of malicious activity in this situation are
  // "Add OAuth2PermissionGrant" and "Add service principal", extend the filter below to capture these too
  | where OperationName has "Consent to application"
  | extend InitiatedBy = iff(isnotempty(tostring(InitiatedBy.user.userPrincipalName)),
            tostring(InitiatedBy.user.userPrincipalName), tostring(InitiatedBy.app.displayName))
  | mv-apply TargetResource = TargetResources on 
    (
        where TargetResource.type =~ "ServicePrincipal"
        | extend TargetResourceName = tolower(tostring(TargetResource.displayName))
    )
  | summarize max(TimeGenerated), OperationCount = count() by OperationName, InitiatedBy, TargetResourceName
  // only including operations initiated by a user or app that is above the threshold so we produce only rare and has not occurred in last 7 days
  | where OperationCount > threshold;
  // Gather current period of audit data
  let RecentConsent = AuditLogs | where TimeGenerated >= ago(current)
  | where OperationName has "Consent to application"
  | extend IpAddress = case(
                isnotempty(tostring(InitiatedBy.user.ipAddress)) and tostring(InitiatedBy.user.ipAddress) != 'null', tostring(InitiatedBy.user.ipAddress),
                isnotempty(tostring(InitiatedBy.app.ipAddress)) and tostring(InitiatedBy.app.ipAddress) != 'null', tostring(InitiatedBy.app.ipAddress),
                'Not Available')
  | extend InitiatedBy = iff(isnotempty(tostring(InitiatedBy.user.userPrincipalName)),
                            tostring(InitiatedBy.user.userPrincipalName), tostring(InitiatedBy.app.displayName))
  | mv-apply TargetResource = TargetResources on 
    (
        where TargetResource.type =~ "ServicePrincipal"
        | extend TargetResourceName = tolower(tostring(TargetResource.displayName)),
                 props = TargetResource.modifiedProperties
    )
  | parse props with * "ConsentType: " ConsentType "]" *
  | mv-apply AdditionalDetail = AdditionalDetails on 
    (
        where AdditionalDetail.key =~ "User-Agent"
        | extend UserAgent = tostring(AdditionalDetail.value)
    )
  | project TimeGenerated, InitiatedBy, IpAddress, TargetResourceName, Category, OperationName, ConsentType, UserAgent, CorrelationId, Type;
  // Exclude previously seen audit activity for "Consent to application" that was seen in the lookback period
  // First for rare InitiatedBy
  let RareConsentBy = RecentConsent | join kind= leftanti AuditTrail on OperationName, InitiatedBy
  | extend Reason = "Previously unseen user consenting";
  // Second for rare TargetResourceName
  let RareConsentApp = RecentConsent | join kind= leftanti AuditTrail on OperationName, TargetResourceName
  | extend Reason = "Previously unseen app granted consent";
  RareConsentBy | union RareConsentApp
  | summarize Reason = make_set(Reason,100) by TimeGenerated, InitiatedBy, IpAddress, TargetResourceName, Category, OperationName, ConsentType, UserAgent, CorrelationId, Type
  | extend timestamp = TimeGenerated, Name = tolower(tostring(split(InitiatedBy,'@',0)[0])), UPNSuffix = tolower(tostring(split(InitiatedBy,'@',1)[0]))
entityMappings:
  - entityType: Account
    fieldMappings:
      - identifier: FullName
        columnName: InitiatedBy
      - identifier: Name
        columnName: Name
      - identifier: UPNSuffix
        columnName: UPNSuffix
  - entityType: CloudApplication
    fieldMappings:
      - identifier: Name
        columnName: TargetResourceName
  - entityType: IP
    fieldMappings:
      - identifier: Address
        columnName: IpAddress
version: 1.1.5
kind: Scheduled