Local Admin Group Changes

Status: available
Severity: high
Time window: 1h
Group by: AddedAccountSID, NewUserSID, OnPremSid
Source: github.com/Azure/Azure-Sentinel

This query searches for changes to the local administrators group. Blogpost: https://www.verboon.info/2020/09/hunting-for-local-group-membership-changes.

MITRE ATT&CK coverage

Tactic	Techniques
Persistence	`T1098` Account Manipulation

Event coverage

Provider	Event/ActionType	Title
Security-Auditing	Event ID 4720	A user account was created.
Security-Auditing	Event ID 4732	A member was added to a security-enabled local group.
Security-Auditing	Event ID 4738	A user account was changed.
Defender-DeviceEvents	UserAccountAddedToLocalGroup	User account added to local group

Rule body kusto

id: 63aa43c2-e88e-4102-aea5-0432851c541a
name: Local Admin Group Changes
description: | 
  This query searches for changes to the local administrators group.
  Blogpost: https://www.verboon.info/2020/09/hunting-for-local-group-membership-changes.
severity: High
status: Available
requiredDataConnectors:
  - connectorId: MicrosoftThreatProtection
    dataTypes:
      - IdentityInfo
      - DeviceEvents
queryFrequency: 1h
queryPeriod: 1h
triggerOperator: gt
triggerThreshold: 0
tactics:
  - Persistence
relevantTechniques:
  - T1098
query: |
  let machineAccountSIDs = dynamic([
    "S-1-5-18",
    "S-1-5-20",
    "S-1-5-19"]);
  let ADAZUsers =  IdentityInfo 
  | extend DirectoryDomain = AccountDomain 
  | extend DirectoryAccount = AccountName 
  | extend OnPremSid = AccountSID
  | distinct DirectoryDomain , DirectoryAccount , OnPremSid , AccountCloudSID, AccountUPN, GivenName, Surname;
   // check for any new created or modified local accounts 
  let NewUsers =  DeviceEvents
  | where ActionType contains "UserAccountCreated" or ActionType contains "UserAccountModified"
  | extend lUserAdded = AccountName
  | extend NewUserSID = AccountSid
  | extend laccountdomain = AccountDomain
  | distinct NewUserSID, lUserAdded,laccountdomain;
  // Check for any local group changes and enrich the data with the account name obtained from the previous query
  DeviceEvents 
  | where ActionType == 'UserAccountAddedToLocalGroup'
  // Exclude machine and wellknown SIDs 
  | where (AccountSid !in (machineAccountSIDs)) and (AccountSid matches regex @"S-\d-\d+-\d+-(\d+-){1,5}\d+")
  | extend LocalGroupSID = tostring(parse_json(AdditionalFields).GroupSid)
  | extend LocalGroup = tostring(parse_json(AdditionalFields).GroupName)
  | extend AddedAccountSID = AccountSid
  | extend Actor = trim(@"[^\w]+",InitiatingProcessAccountName)
  // limit to local administrators group
  // | where LocalGroupSID contains "S-1-5-32-544"
  | join kind=leftouter    (NewUsers)
  on $left.AddedAccountSID == $right.NewUserSID
  | project TimeGenerated, DeviceName, LocalGroup,LocalGroupSID, AddedAccountSID, lUserAdded , Actor, ActionType , laccountdomain 
  | join kind=innerunique  (ADAZUsers)
  on $left.AddedAccountSID == $right.OnPremSid
  | extend UserAdded = iff(isnotempty(lUserAdded),strcat(laccountdomain,"\\", lUserAdded), strcat(DirectoryDomain,"\\", DirectoryAccount))
  | extend AccountName = iff(isnotempty(lUserAdded), lUserAdded, DirectoryAccount)
  | project TimeGenerated, DeviceName, LocalGroup, LocalGroupSID, AddedAccountSID, UserAdded ,Actor, ActionType, AccountName, laccountdomain  
  | where DeviceName !contains Actor
  // Provide details on actors that added users
  // | summarize count()  by Actor 
  // | join ADAZUsers
  // on $left.Actor == $right.DirectoryAccount 
  // | render piechart
  | extend HostName = iff(DeviceName has '.', substring(DeviceName, 0, indexof(DeviceName, '.')), DeviceName)
  | extend DnsDomain = iff(DeviceName has '.', substring(DeviceName, indexof(DeviceName, '.') + 1), "")
entityMappings:
  - entityType: Host
    fieldMappings:
      - identifier: FullName
        columnName: DeviceName
      - identifier: HostName
        columnName: HostName
      - identifier: DnsDomain
        columnName: DnsDomain
  - entityType: Account
    fieldMappings:
      - identifier: FullName
        columnName: UserAdded
      - identifier: Name
        columnName: AccountName
      - identifier: NTDomain
        columnName: laccountdomain
version: 1.0.2
kind: Scheduled

Stages and Predicates

Let binding: `machineAccountSIDs`

let machineAccountSIDs = dynamic([
  "S-1-5-18",
  "S-1-5-20",
  "S-1-5-19"]);

Let binding: `ADAZUsers`

let ADAZUsers = IdentityInfo 
| extend DirectoryDomain = AccountDomain 
| extend DirectoryAccount = AccountName 
| extend OnPremSid = AccountSID
| distinct DirectoryDomain , DirectoryAccount , OnPremSid , AccountCloudSID, AccountUPN, GivenName, Surname;

Let binding: `NewUsers`

let NewUsers = DeviceEvents
| where ActionType contains "UserAccountCreated" or ActionType contains "UserAccountModified"
| extend lUserAdded = AccountName
| extend NewUserSID = AccountSid
| extend laccountdomain = AccountDomain
| distinct NewUserSID, lUserAdded,laccountdomain;

Stage 1: `source`

DeviceEvents

Stage 2: `where`

| where ActionType == 'UserAccountAddedToLocalGroup'

Stage 3: `where`

| where (AccountSid !in (machineAccountSIDs)) and (AccountSid matches regex @"S-\d-\d+-\d+-(\d+-){1,5}\d+")

References machineAccountSIDs (defined above).

Stage 4: `extend` (4 consecutive steps)

| extend LocalGroupSID = tostring(parse_json(AdditionalFields).GroupSid)
| extend LocalGroup = tostring(parse_json(AdditionalFields).GroupName)
| extend AddedAccountSID = AccountSid
| extend Actor = trim(@"[^\w]+",InitiatingProcessAccountName)

Stage 5: `join`

| join kind=leftouter    (NewUsers)
on $left.AddedAccountSID == $right.NewUserSID

Stage 6: `project`

| project TimeGenerated, DeviceName, LocalGroup,LocalGroupSID, AddedAccountSID, lUserAdded , Actor, ActionType , laccountdomain

Stage 7: `join`

| join kind=innerunique  (ADAZUsers)
on $left.AddedAccountSID == $right.OnPremSid

Stage 8: `extend`

| extend UserAdded = iff(isnotempty(lUserAdded),strcat(laccountdomain,"\\", lUserAdded), strcat(DirectoryDomain,"\\", DirectoryAccount))

UserAdded =

ifisnotempty(lUserAdded)strcat(laccountdomain, "\\", lUserAdded)

elsestrcat(DirectoryDomain, "\\", DirectoryAccount)

Stage 9: `extend`

| extend AccountName = iff(isnotempty(lUserAdded), lUserAdded, DirectoryAccount)

AccountName =

ifisnotempty(lUserAdded)lUserAdded

elseDirectoryAccount

Stage 10: `project`

| project TimeGenerated, DeviceName, LocalGroup, LocalGroupSID, AddedAccountSID, UserAdded ,Actor, ActionType, AccountName, laccountdomain

Stage 11: `where`

| where DeviceName !contains Actor

Stage 12: `extend`

| extend HostName = iff(DeviceName has '.', substring(DeviceName, 0, indexof(DeviceName, '.')), DeviceName)

HostName =

ifDeviceName has "."substring(DeviceName, 0, indexof(DeviceName, '.'))

elseDeviceName

Stage 13: `extend`

| extend DnsDomain = iff(DeviceName has '.', substring(DeviceName, indexof(DeviceName, '.') + 1), "")

DnsDomain =

ifDeviceName has "."substring(DeviceName, (indexof(DeviceName, '.') + 1))

else""

Exclusions

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

Field	Kind	Excluded values
`AccountSid`	in	`S-1-5-18`, `S-1-5-19`, `S-1-5-20`
`DeviceName`	contains	`Actor`

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
`AccountSid`	regex_match	`S-\d-\d+-\d+-(\d+-){1,5}\d+`
`ActionType`	contains	`UserAccountCreated` `UserAccountModified`
`ActionType`	eq	`UserAccountAddedToLocalGroup` 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
`AccountName`	`project`
`ActionType`	`project`
`Actor`	`project`
`AddedAccountSID`	`project`
`DeviceName`	`project`
`LocalGroup`	`project`
`LocalGroupSID`	`project`
`TimeGenerated`	`project`
`UserAdded`	`project`
`laccountdomain`	`project`
`HostName`	`extend`
`DnsDomain`	`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)

Local Admin Group Changes

MITRE ATT&CK coverage

Event coverage

Rule body kusto

Stages and Predicates

Let binding: `machineAccountSIDs`

Let binding: `ADAZUsers`

Let binding: `NewUsers`

Stage 1: `source`

Stage 2: `where`

Stage 3: `where`

Stage 4: `extend` (4 consecutive steps)

Stage 5: `join`

Stage 6: `project`

Stage 7: `join`

Stage 8: `extend`

Stage 9: `extend`

Stage 10: `project`

Stage 11: `where`

Stage 12: `extend`

Stage 13: `extend`

Exclusions

Indicators

Output fields

Keyboard shortcuts

Search operators

Local Admin Group Changes

MITRE ATT&CK coverage

Event coverage

Rule body kusto

Stages and Predicates

Let binding: machineAccountSIDs

Let binding: ADAZUsers

Let binding: NewUsers

Stage 1: source

Stage 2: where

Stage 3: where

Stage 4: extend (4 consecutive steps)

Stage 5: join

Stage 6: project

Stage 7: join

Stage 8: extend

Stage 9: extend

Stage 10: project

Stage 11: where

Stage 12: extend

Stage 13: extend

Exclusions

Indicators

Output fields

Let binding: `machineAccountSIDs`

Let binding: `ADAZUsers`

Let binding: `NewUsers`

Stage 1: `source`

Stage 2: `where`

Stage 3: `where`

Stage 4: `extend` (4 consecutive steps)

Stage 5: `join`

Stage 6: `project`

Stage 7: `join`

Stage 8: `extend`

Stage 9: `extend`

Stage 10: `project`

Stage 11: `where`

Stage 12: `extend`

Stage 13: `extend`