Detections/SecurityEvent/UserCreatedAddedToBuiltinAdmins_1d.yaml

id: aa1eff90-29d4-49dc-a3ea-b65199f516db
name: New user created and added to the built-in administrators group
description: |
  'Identifies when a user account was created and then added to the builtin Administrators group in the same day.
  This should be monitored closely and all additions reviewed.'
severity: Low
requiredDataConnectors:
  - connectorId: SecurityEvents
    dataTypes:
     - SecurityEvent
  - connectorId: WindowsSecurityEvents
    dataTypes: 
      - SecurityEvents 
  - connectorId: WindowsForwardedEvents
    dataTypes: 
      - WindowsEvent 
queryFrequency: 1d
queryPeriod: 1d
triggerOperator: gt
triggerThreshold: 0
tactics:
  - Persistence
  - PrivilegeEscalation
relevantTechniques:
  - T1098
  - T1078
query: |
  (union isfuzzy=true
      (SecurityEvent
      | where EventID == 4720
      | where AccountType == "User"
      | project CreatedUserTime = TimeGenerated, CreatedUserEventID = EventID, CreatedUserActivity = Activity, Computer = toupper(Computer), 
      CreatedUser = tolower(TargetAccount), CreatedUserAccountName = TargetUserName, CreatedUserDomainName = TargetDomainName, CreatedUserSid = TargetSid, 
      AccountUsedToCreateUser = SubjectAccount, CreatedByAccountName = SubjectUserName, CreatedByDomainName = SubjectDomainName, SidofAccountUsedToCreateUser = SubjectUserSid
      ),
      (WindowsEvent
      | where EventID == 4720
      | extend SubjectUserSid = tostring(EventData.SubjectUserSid)
      | extend AccountType=case(EventData.SubjectUserName endswith "$" or SubjectUserSid in ("S-1-5-18", "S-1-5-19", "S-1-5-20"), "Machine", isempty(SubjectUserSid), "", "User")
      | where AccountType == "User"
      | extend SubjectAccount = strcat(tostring(EventData.SubjectDomainName),"\\", tostring(EventData.SubjectUserName))
      | extend SubjectDomainName = tostring(EventData.SubjectDomainName), SubjectUserName = tostring(EventData.SubjectUserName)
      | extend TargetAccount = strcat(EventData.TargetDomainName,"\\", EventData.TargetUserName)
      | extend TargetUserName = tostring(EventData.TargetUserName), TargetDomainName = tostring(EventData.TargetDomainName) 
      | extend Activity="4720 - A user account was created."
      | extend TargetSid = tostring(EventData.TargetSid)
      | project CreatedUserTime = TimeGenerated, CreatedUserEventID = EventID, CreatedUserActivity = Activity, Computer = toupper(Computer), 
      CreatedUser = tolower(TargetAccount), CreatedUserAccountName = TargetUserName, CreatedUserDomainName = TargetDomainName, CreatedUserSid = TargetSid, 
      AccountUsedToCreateUser = SubjectAccount, CreatedByAccountName = SubjectUserName, CreatedByDomainName = SubjectDomainName, SidofAccountUsedToCreateUser = SubjectUserSid
      )
    )
  | join kind=inner
  (
    (union isfuzzy=true
      (SecurityEvent 
      | where AccountType == "User"
      // 4732 - A member was added to a security-enabled local group
      | where EventID == 4732
      // TargetSid is the builin Admins group: S-1-5-32-544
      | where TargetSid == "S-1-5-32-544"
      | project GroupAddTime = TimeGenerated, GroupAddEventID = EventID, GroupAddActivity = Activity, Computer = toupper(Computer), GroupName = tolower(TargetAccount), 
      GroupSid = TargetSid, AccountThatAddedUser = SubjectAccount, SIDofAccountThatAddedUser = SubjectUserSid, AddedByAccountName = SubjectUserName, AddedByDomainName = SubjectDomainName,
      CreatedUserSid = MemberSid
      ),
      (  WindowsEvent 
      // 4732 - A member was added to a security-enabled local group
      | where EventID == 4732 and EventData has "S-1-5-32-544"
      //TargetSid is the builin Admins group: S-1-5-32-544
      | extend SubjectUserSid = tostring(EventData.SubjectUserSid)
      | extend AccountType=case(EventData.SubjectUserName endswith "$" or SubjectUserSid in ("S-1-5-18", "S-1-5-19", "S-1-5-20"), "Machine", isempty(SubjectUserSid), "", "User")
      | where AccountType == "User"
      | extend TargetSid = tostring(EventData.TargetSid)
      | where TargetSid == "S-1-5-32-544"
      | extend SubjectAccount = strcat(tostring(EventData.SubjectDomainName),"\\", tostring(EventData.SubjectUserName))
      | extend SubjectDomainName = tostring(EventData.SubjectDomainName), SubjectUserName = tostring(EventData.SubjectUserName)
      | extend TargetAccount = strcat(EventData.TargetDomainName,"\\", EventData.TargetUserName)
      | extend Activity="4732 - A member was added to a security-enabled local group."
      | extend MemberSid = tostring(EventData.MemberSid)
      | project GroupAddTime = TimeGenerated, GroupAddEventID = EventID, GroupAddActivity = Activity, Computer = toupper(Computer), GroupName = tolower(TargetAccount), 
      GroupSid = TargetSid, AccountThatAddedUser = SubjectAccount, SIDofAccountThatAddedUser = SubjectUserSid, AddedByAccountName = SubjectUserName, AddedByDomainName = SubjectDomainName,
      CreatedUserSid = MemberSid
      )
    )
  )
  on CreatedUserSid
  //Create User first, then the add to the group.
  | project Computer, CreatedUserTime, CreatedUserEventID, CreatedUserActivity, CreatedUser, CreatedUserSid, CreatedUserAccountName, CreatedUserDomainName,
  GroupAddTime, GroupAddEventID, GroupAddActivity, GroupName, GroupSid,
  AccountUsedToCreateUser, SidofAccountUsedToCreateUser, CreatedByAccountName, CreatedByDomainName, 
  AccountThatAddedUser, SIDofAccountThatAddedUser, AddedByAccountName, AddedByDomainName
  | extend HostName = tostring(split(Computer, ".")[0]), DomainIndex = toint(indexof(Computer, '.'))
  | extend HostNameDomain = iff(DomainIndex != -1, substring(Computer, DomainIndex + 1), Computer)
  | project-away DomainIndex
entityMappings:
  - entityType: Account
    fieldMappings:
      - identifier: FullName
        columnName: AccountUsedToCreateUser
      - identifier: Name
        columnName: CreatedByAccountName
      - identifier: NTDomain
        columnName: CreatedByDomainName
  - entityType: Account
    fieldMappings:
      - identifier: FullName
        columnName: AccountThatAddedUser
      - identifier: Name
        columnName: AddedByAccountName
      - identifier: NTDomain
        columnName: AddedByDomainName
  - entityType: Account
    fieldMappings:
      - identifier: FullName
        columnName: CreatedUser
      - identifier: Name
        columnName: CreatedUserAccountName
      - identifier: NTDomain
        columnName: CreatedUserDomainName
  - entityType: Account
    fieldMappings:
      - identifier: Sid
        columnName: CreatedUserSid
  - entityType: Host
    fieldMappings:
      - identifier: FullName
        columnName: Computer
      - identifier: HostName
        columnName: HostName
      - identifier: NTDomain
        columnName: HostNameDomain
version: 1.2.1
kind: Scheduled
metadata:
    source:
        kind: Community
    author:
        name: Microsoft Security Research
    support:
        tier: Community
    categories:
        domains: [ "Security - Others", "Identity" ]