Conditional Access - Dynamic Group Exclusion Changes

Severity: high
Time window: 5m
Source: github.com/Azure/Azure-Sentinel

// Detects changes to Dynamic Membership Rules for specified groups (often used in CA exclusions)

MITRE ATT&CK coverage

Tactic	Techniques
Privilege Escalation	`T1484` Domain or Tenant Policy Modification

Event coverage

Provider	Event
Entra-AuditLogs	Update group

Rule body kusto

id: c385944b-17b9-4b2b-921e-0e8d0341a675
name: Conditional Access - Dynamic Group Exclusion Changes
version: 1.0.1
kind: Scheduled
description: // Detects changes to Dynamic Membership Rules for specified groups (often used in CA exclusions)
severity: High
requiredDataConnectors:
  - connectorId: AzureActiveDirectory
    dataTypes:
      - AuditLogs
queryFrequency: 5m
queryPeriod: 5m
triggerOperator: gt
triggerThreshold: 0
tactics:
- PrivilegeEscalation
relevantTechniques:
- T1484
query: |-
  // Detects changes to Dynamic Membership Rules for specified groups (often used in CA exclusions)
  let monitoredGroups = dynamic(["Group1", "Group2"]);  // <-- Customize this list
  AuditLogs
  | where OperationName == "Update group"
  | where AdditionalDetails[0].value == "DynamicMembership"
  | extend DynamicGroupName = tostring(TargetResources[0].displayName)
  | where DynamicGroupName in (monitoredGroups)
  | extend modifiedBy = tostring(InitiatedBy.user.userPrincipalName)
  | extend accountName = tostring(split(modifiedBy, "@")[0])
  | extend upnSuffix = tostring(split(modifiedBy, "@")[1])
  | extend oldRule = tostring(TargetResources[0].modifiedProperties[0].oldValue)
  | extend newRule = tostring(TargetResources[0].modifiedProperties[0].newValue)
  | where oldRule != newRule
  | project
      TimeGenerated,
      OperationName,
      DynamicGroupName,
      modifiedBy,
      accountName,
      upnSuffix,
      result = Result,
      oldRule,
      newRule
  | order by TimeGenerated desc
entityMappings:
- entityType: Account
  fieldMappings:
  - identifier: Name
    columnName: accountName
  - identifier: UPNSuffix
    columnName: upnSuffix
suppressionEnabled: false
suppressionDuration: 5h
eventGroupingSettings:
  aggregationKind: AlertPerResult
incidentConfiguration:
  createIncident: true
  groupingConfiguration:
    enabled: false
    reopenClosedIncident: false
    lookbackDuration: PT5H
    matchingMethod: AllEntities
    groupByEntities: []
    groupByAlertDetails: []
    groupByCustomDetails: []

Stages and Predicates

Parameters

let monitoredGroups = dynamic(["Group1", "Group2"]);

Stage 1: `source`

AuditLogs

Stage 2: `where`

| where OperationName == "Update group"

Stage 3: `where`

| where AdditionalDetails[0].value == "DynamicMembership"

Stage 4: `extend`

| extend DynamicGroupName = tostring(TargetResources[0].displayName)

Stage 5: `where`

| where DynamicGroupName in (monitoredGroups)

Stage 6: `extend` (5 consecutive steps)

| extend modifiedBy = tostring(InitiatedBy.user.userPrincipalName)
| extend accountName = tostring(split(modifiedBy, "@")[0])
| extend upnSuffix = tostring(split(modifiedBy, "@")[1])
| extend oldRule = tostring(TargetResources[0].modifiedProperties[0].oldValue)
| extend newRule = tostring(TargetResources[0].modifiedProperties[0].newValue)

Stage 7: `where`

| where oldRule != newRule

Stage 8: `project`

| project
    TimeGenerated,
    OperationName,
    DynamicGroupName,
    modifiedBy,
    accountName,
    upnSuffix,
    result = Result,
    oldRule,
    newRule

Stage 9: `sort`

| order by TimeGenerated desc

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
`DynamicGroupName`	in	`Group1` transforms: `cased` `Group2` transforms: `cased`
`OperationName`	eq	`Update group` transforms: `cased`
`oldRule`	ne	`newRule` transforms: `cased`
`value`	eq	`DynamicMembership` 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
`DynamicGroupName`	`project`
`OperationName`	`project`
`TimeGenerated`	`project`
`accountName`	`project`
`modifiedBy`	`project`
`newRule`	`project`
`oldRule`	`project`
`result`	`project`
`upnSuffix`	`project`

`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)

Conditional Access - Dynamic Group Exclusion Changes

MITRE ATT&CK coverage

Event coverage

Rule body kusto

Stages and Predicates

Parameters

Stage 1: `source`

Stage 2: `where`

Stage 3: `where`

Stage 4: `extend`

Stage 5: `where`

Stage 6: `extend` (5 consecutive steps)

Stage 7: `where`

Stage 8: `project`

Stage 9: `sort`

Indicators

Output fields

Keyboard shortcuts

Search operators

Conditional Access - Dynamic Group Exclusion Changes

MITRE ATT&CK coverage

Event coverage

Rule body kusto

Stages and Predicates

Parameters

Stage 1: source

Stage 2: where

Stage 3: where

Stage 4: extend

Stage 5: where

Stage 6: extend (5 consecutive steps)

Stage 7: where

Stage 8: project

Stage 9: sort

Indicators

Output fields

Stage 1: `source`

Stage 2: `where`

Stage 3: `where`

Stage 4: `extend`

Stage 5: `where`

Stage 6: `extend` (5 consecutive steps)

Stage 7: `where`

Stage 8: `project`

Stage 9: `sort`