Cross-tenant Access Settings Organization Added

Status: available
Severity: medium
Time window: 2d
Source: github.com/Azure/Azure-Sentinel

Organizations are added in the Cross-tenant Access Settings to control communication inbound or outbound for users and applications. This detection notifies when an Organization is added other than the list that is supposed to exist from the Microsoft Entra ID Cross-tenant Access Settings.

MITRE ATT&CK coverage

Tactic	Techniques
Initial Access	`T1078.004` Valid Accounts: Cloud Accounts
Persistence	`T1078.004` Valid Accounts: Cloud Accounts, `T1136.003` Create Account: Cloud Account
Discovery	`T1087.004` Account Discovery: Cloud Account

Event coverage

Provider	Event	Title
Entra-AuditLogs	_catch_all	Entra ID audit event (any operation)

Rule body kusto

id: 757e6a79-6d23-4ae6-9845-4dac170656b5
name: Cross-tenant Access Settings Organization Added
description: |
  'Organizations are added in the Cross-tenant Access Settings to control communication inbound or outbound for users and applications. This detection notifies when an Organization is added other than the list that is supposed to exist from the Microsoft Entra ID Cross-tenant Access Settings.'
severity: Medium
requiredDataConnectors:
  - connectorId: AzureActiveDirectory
    dataTypes:
      - AuditLogs
queryFrequency: 2d
queryPeriod: 2d
triggerOperator: gt
triggerThreshold: 0
status: Available
tactics:
  - InitialAccess
  - Persistence
  - Discovery
relevantTechniques:
  - T1078.004
  - T1136.003
  - T1087.004
query: |
  // Tenants IDs can be found by navigating to Azure Active Directory then from menu on the left, select External Identities, then from menu on the left, select Cross-tenant access settings and from the list shown of Tenants
  let ExpectedTenantIDs = dynamic(["List of expected tenant IDs","Tenant ID 2"]);
  AuditLogs
  | where OperationName has "Add a partner to cross-tenant access setting"
  | mv-apply TargetResource = TargetResources on
    (
        where TargetResource.type =~ "Policy"
        | extend Properties = TargetResource.modifiedProperties
    )
  | mv-apply Property = Properties on
    (
        where Property.displayName =~ "tenantId"
        | extend ExtTenantIDAdded = trim('"',tostring(Property.newValue))
    )
  | where ExtTenantIDAdded !in (ExpectedTenantIDs)
  | extend InitiatingAppName = tostring(InitiatedBy.app.displayName)
  | extend InitiatingAppServicePrincipalId = tostring(InitiatedBy.app.servicePrincipalId)
  | extend InitiatingUserPrincipalName = tostring(InitiatedBy.user.userPrincipalName)
  | extend InitiatingAadUserId = tostring(InitiatedBy.user.id)
  | extend InitiatingIpAddress = tostring(iff(isnotempty(InitiatedBy.user.ipAddress), InitiatedBy.user.ipAddress, InitiatedBy.app.ipAddress))
  | extend InitiatingAccountName = tostring(split(InitiatingUserPrincipalName, "@")[0]), InitiatingAccountUPNSuffix = tostring(split(InitiatingUserPrincipalName, "@")[1])
entityMappings:
  - entityType: Account
    fieldMappings:
      - identifier: Name
        columnName: InitiatingAppName
      - identifier: AadUserId
        columnName: InitiatingAppServicePrincipalId
  - entityType: Account
    fieldMappings:
      - identifier: FullName
        columnName: InitiatingUserPrincipalName
      - identifier: Name
        columnName: InitiatingAccountName
      - identifier: UPNSuffix
        columnName: InitiatingAccountUPNSuffix
  - entityType: Account
    fieldMappings:
      - identifier: AadUserId
        columnName: InitiatingAadUserId
  - entityType: IP
    fieldMappings:
      - identifier: Address
        columnName: InitiatingIpAddress
version: 1.1.1
kind: Scheduled

Stages and Predicates

Parameters

let ExpectedTenantIDs = dynamic(["List of expected tenant IDs","Tenant ID 2"]);

Stage 1: `source`

AuditLogs

Stage 2: `where`

| where OperationName has "Add a partner to cross-tenant access setting"

Stage 3: `kusto:mv-apply`

| mv-apply TargetResource = TargetResources on
  (
      where TargetResource.type =~ "Policy"
      | extend Properties = TargetResource.modifiedProperties
  )

Stage 4: `kusto:mv-apply`

| mv-apply Property = Properties on
  (
      where Property.displayName =~ "tenantId"
      | extend ExtTenantIDAdded = trim('"',tostring(Property.newValue))
  )

Stage 5: `where`

| where ExtTenantIDAdded !in (ExpectedTenantIDs)

Stage 6: `extend` (6 consecutive steps)

| extend InitiatingAppName = tostring(InitiatedBy.app.displayName)
| extend InitiatingAppServicePrincipalId = tostring(InitiatedBy.app.servicePrincipalId)
| extend InitiatingUserPrincipalName = tostring(InitiatedBy.user.userPrincipalName)
| extend InitiatingAadUserId = tostring(InitiatedBy.user.id)
| extend InitiatingIpAddress = tostring(iff(isnotempty(InitiatedBy.user.ipAddress), InitiatedBy.user.ipAddress, InitiatedBy.app.ipAddress))
| extend InitiatingAccountName = tostring(split(InitiatingUserPrincipalName, "@")[0]), InitiatingAccountUPNSuffix = tostring(split(InitiatingUserPrincipalName, "@")[1])

Exclusions

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

Field	Kind	Excluded values
`ExtTenantIDAdded`	in	`List of expected tenant IDs`, `Tenant ID 2`

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.

Field	Kind	Values
`OperationName`	match	`Add a partner to cross-tenant access setting` transforms: `term`
`displayName`	eq	`tenantId`
`type`	eq	`Policy`

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.

Field	Source
`InitiatingAppName`	`extend`
`InitiatingAppServicePrincipalId`	`extend`
`InitiatingUserPrincipalName`	`extend`
`InitiatingAadUserId`	`extend`
`InitiatingIpAddress`	`extend`
`InitiatingAccountName`	`extend`
`InitiatingAccountUPNSuffix`	`extend`

`j` / `k`	Scroll down / up
`d` / `u`	Half-page down / up
`gg` / `G`	Top / bottom
`h` / `l`	History back / forward
`f`	Follow link (`Shift` = new tab)
`/`	Focus search
`?`	Toggle this help
`↑` / `↓`	Navigate search results
`Enter`	Open highlighted result
`Esc`	Close results / dialog

`type:`	`events` / `rules` / `providers`
`vendor:`	`sigma` / `elastic` / `splunk` / `kusto` / `chronicle` (vendor name alone also works: `sigma:`, `kql:`, `secops:`…)
`tactic:`	TA-id, slug, or name: `credential_access`, `TA0006`
`technique:`	technique or sub-technique ID: `T1003`, `T1003.001` (alias `tech:`)
`severity:`	`critical` / `high` / `medium` / `low` / `informational` (alias `sev:`)
`risk_score`	Numeric comparison on the Elastic risk score (0 to 100): `risk_score>50`, `risk_score<=20`, `risk_score=99` (alias `risk`; Elastic rules only)
`stages:`	Rules with exactly N pipeline stages
`correlation:`	`single_event` / `sequence` / `alternatives` / `alternatives_cross_log` / `all_required` / `correlated`
`with:`	Co-occurrence event-id; stacks (`with:4624 with:4769`) to require all, while a comma list in one occurrence (`with:4624,4769`) is an either-or group. Implies multi-event
`like:`	Structural neighbors of a rule slug (equivalents + subsumption stricter / broader): `like:comsvcs_lsass_memory_dump-splunk-sysmon`
`groupby:`	Entity-grouping substring match against `group_by_keys`: `groupby:user`, `groupby:host`
`uses:`	Rules whose predicate tree touches the field (any kind, any value): `uses:CommandLine`
`excludes:`	Rules with top-level `not()` clauses on the field (FP whitelists): `excludes:ParentImage`
`field:` / `value:`	Predicate search; narrows rule cards to those with a matching leaf and drives the indicator tier. Unquoted = substring, wildcards allowed (`value:mimikatz`)
`indicator:`	Shorthand for `field:F value:V`: `indicator:Image=*\powershell.exe`
`kind:`	Filter by predicate kind. Narrows rule cards to those carrying a matching predicate leaf (`vendor:elastic kind:cidr_match`) and drives the indicator tier: `contains` / `starts_with` / `ends_with` / `regex` / `cidr` / `eq` / `in` … (operator aliases `op:`/`match:`)
`has:` / `no:`	`sample`, `field`, `notes`, `refs`, `trace`, `thirdparty`, `rule`, `pattern`, `timewindow`, `threshold`, `newterms`, `sigma`/`elastic`/`splunk`/`kusto`/`chronicle`
`-op:val`	Exclude matches; works on most operators but not `type:`/`like:`/`has:`/`no:` (use `no:<flag>` to exclude a rule flag): `tactic:execution -vendor:splunk`. Standalone `-kind:`/`-field:`/`-value:` drop every rule carrying a matching predicate leaf (`type:rules -kind:is_null`)
`field:"…"` / `value:"…"`	Quoted value = anchored exact match (also allows spaces): `value:"net user"`
`a,b`	Comma = OR inside one operator (`vendor:sigma,elastic`, `severity:high,critical`); repeating a facet merges the same way. `field:`/`value:` never split (literal commas)
`vendors:` / `stage:`	Singular and plural spellings fold to the canonical operator and value: `tactics:` = `tactic:`, `type:event` = `type:events`, `correlation:sequences` = `correlation:sequence`, `has:thresholds` = `has:threshold`
`"quoted phrase"`	Exact-match a multi-word phrase (free text)

Cross-tenant Access Settings Organization Added

MITRE ATT&CK coverage

Event coverage

Rule body kusto

Stages and Predicates

Parameters

Stage 1: `source`

Stage 2: `where`

Stage 3: `kusto:mv-apply`

Stage 4: `kusto:mv-apply`

Stage 5: `where`

Stage 6: `extend` (6 consecutive steps)

Exclusions

Indicators

Output fields

Keyboard shortcuts

Search operators

Cross-tenant Access Settings Organization Added

MITRE ATT&CK coverage

Event coverage

Rule body kusto

Stages and Predicates

Parameters

Stage 1: source

Stage 2: where

Stage 3: kusto:mv-apply

Stage 4: kusto:mv-apply

Stage 5: where

Stage 6: extend (6 consecutive steps)

Exclusions

Indicators

Output fields

Stage 1: `source`

Stage 2: `where`

Stage 3: `kusto:mv-apply`

Stage 4: `kusto:mv-apply`

Stage 5: `where`

Stage 6: `extend` (6 consecutive steps)