New onmicrosoft domain added to tenant

Status: available
Severity: medium
Time window: 1h
Source: github.com/Azure/Azure-Sentinel

This detection looks for new onmicrosoft domains being added to a tenant. An attacker who compromises a tenant may register a new onmicrosoft domain in order to masquerade as a service provider for launching phishing campaigns. Domain additions are not a common occurrence and users should validate that the domain was added by a legitimate user, with a legitimate purpose.

MITRE ATT&CK coverage

Tactic	Techniques
Resource Development	`T1585.003` Establish Accounts: Cloud Accounts

Event coverage

Provider	Event
Entra-AuditLogs	Add unverified domain
Entra-AuditLogs	Add verified domain

Rule body kusto

id: 4f42b94f-b210-42d1-a023-7fa1c51d969f
name: New onmicrosoft domain added to tenant
description: |
  'This detection looks for new onmicrosoft domains being added to a tenant. 
  An attacker who compromises a tenant may register a new onmicrosoft domain in order to masquerade as a service provider for launching phishing campaigns.
  Domain additions are not a common occurrence and users should validate that the domain was added by a legitimate user, with a legitimate purpose.'
severity: Medium
requiredDataConnectors:
  - connectorId: AzureActiveDirectory
    dataTypes:
      - AuditLogs
queryFrequency: 1h
queryPeriod: 1h
triggerOperator: gt
triggerThreshold: 0
status: Available
tactics:
  - ResourceDevelopment
relevantTechniques:
  - T1585.003
query: |
  AuditLogs
  | where AADOperationType == "Add"
  | where Result == "success"
  | where OperationName in ("Add verified domain", "Add unverified domain")
  | extend InitiatedBy = parse_json(InitiatedBy)
  | extend InitiatingUser = tostring(InitiatedBy.user.userPrincipalName)
  | extend InitiatingAadUserId = tostring(InitiatedBy.user.id)
  | extend InitiatingIp = tostring(InitiatedBy.user.ipAddress)
  | extend InitiatingApp = tostring(InitiatedBy.app.displayName)
  | extend InitiatingSPID = tostring(InitiatedBy.app.servicePrincipalId)
  | extend DomainAdded = tostring(TargetResources[0].displayName)
  | where DomainAdded has "onmicrosoft"
  | extend ActionInitiatedBy = case(isnotempty(InitiatingUser), InitiatingUser, strcat(InitiatingApp, " - ", InitiatingSPID))
  | extend UserName = split(InitiatingUser, "@")[0]
  | extend UPNSuffix = split(InitiatingUser, "@")[1]
  | project-reorder TimeGenerated, OperationName, DomainAdded, ActionInitiatedBy, InitiatingIp
entityMappings:
  - entityType: Account
    fieldMappings:
      - identifier: FullName
        columnName: InitiatingUser
      - identifier: Name
        columnName: UserName
      - identifier: UPNSuffix
        columnName: UPNSuffix
  - entityType: Account
    fieldMappings:
      - identifier: AadUserId
        columnName: InitiatingAadUserId
  - entityType: Account
    fieldMappings:
      - identifier: AadUserId
        columnName: InitiatingSPID
  - entityType: IP
    fieldMappings:
      - identifier: Address
        columnName: InitiatingIp
  - entityType: DNS
    fieldMappings:
      - identifier: DomainName
        columnName: DomainAdded
eventGroupingSettings:
  aggregationKind: SingleAlert
alertDetailsOverride:
  alertDisplayNameFormat: '{{DomainAdded}} added to tenant by {{ActionInitiatedBy}}'
  alertDescriptionFormat: 'This detection looks for new onmicrosoft domains being added to a tenant. An attacker who compromises a tenant may register a new onmicrosoft domain in order to masquerade as a service provider for launching phishing accounts. Domain additions are not a common occurrence and users should validate that {{ActionInitiatedBy}} added {{DomainAdded}} with a legitimate purpose.'
kind: Scheduled
version: 1.0.1

Stages and Predicates

Stage 1: `source`

AuditLogs

Stage 2: `where`

| where AADOperationType == "Add"

Stage 3: `where`

| where Result == "success"

Stage 4: `where`

| where OperationName in ("Add verified domain", "Add unverified domain")

Stage 5: `extend` (7 consecutive steps)

| extend InitiatedBy = parse_json(InitiatedBy)
| extend InitiatingUser = tostring(InitiatedBy.user.userPrincipalName)
| extend InitiatingAadUserId = tostring(InitiatedBy.user.id)
| extend InitiatingIp = tostring(InitiatedBy.user.ipAddress)
| extend InitiatingApp = tostring(InitiatedBy.app.displayName)
| extend InitiatingSPID = tostring(InitiatedBy.app.servicePrincipalId)
| extend DomainAdded = tostring(TargetResources[0].displayName)

Stage 6: `where`

| where DomainAdded has "onmicrosoft"

Stage 7: `extend` (3 consecutive steps)

| extend ActionInitiatedBy = case(isnotempty(InitiatingUser), InitiatingUser, strcat(InitiatingApp, " - ", InitiatingSPID))
| extend UserName = split(InitiatingUser, "@")[0]
| extend UPNSuffix = split(InitiatingUser, "@")[1]

ActionInitiatedBy =

ifisnotempty(InitiatingUser)InitiatingUser

elsestrcat(InitiatingApp, " - ", InitiatingSPID)

Stage 8: `project-reorder`

| project-reorder TimeGenerated, OperationName, DomainAdded, ActionInitiatedBy, InitiatingIp

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
`AADOperationType`	eq	`Add` transforms: `cased`
`DomainAdded`	match	`onmicrosoft` transforms: `term`
`OperationName`	in	`Add unverified domain` transforms: `cased` `Add verified domain` transforms: `cased`
`Result`	eq	`success` transforms: `cased`

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
`InitiatedBy`	`extend`
`InitiatingUser`	`extend`
`InitiatingAadUserId`	`extend`
`InitiatingIp`	`extend`
`InitiatingApp`	`extend`
`InitiatingSPID`	`extend`
`DomainAdded`	`extend`
`ActionInitiatedBy`	`extend`
`UserName`	`extend`
`UPNSuffix`	`extend`

`j` / `k`	Scroll down / up
`d` / `u`	Half-page down / up
`gg` / `G`	Top / bottom
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`f`	Follow link (`Shift` = new tab)
`/`	Focus search
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`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)

New onmicrosoft domain added to tenant

MITRE ATT&CK coverage

Event coverage

Rule body kusto

Stages and Predicates

Stage 1: `source`

Stage 2: `where`

Stage 3: `where`

Stage 4: `where`

Stage 5: `extend` (7 consecutive steps)

Stage 6: `where`

Stage 7: `extend` (3 consecutive steps)

Stage 8: `project-reorder`

Indicators

Output fields

Keyboard shortcuts

Search operators

New onmicrosoft domain added to tenant

MITRE ATT&CK coverage

Event coverage

Rule body kusto

Stages and Predicates

Stage 1: source

Stage 2: where

Stage 3: where

Stage 4: where

Stage 5: extend (7 consecutive steps)

Stage 6: where

Stage 7: extend (3 consecutive steps)

Stage 8: project-reorder

Indicators

Output fields

Stage 1: `source`

Stage 2: `where`

Stage 3: `where`

Stage 4: `where`

Stage 5: `extend` (7 consecutive steps)

Stage 6: `where`

Stage 7: `extend` (3 consecutive steps)

Stage 8: `project-reorder`