User account added to built in domain local or global group

// For AD SID mappings - https://docs.microsoft.com/windows/security/identity-protection/access-control/active-directory-security-groups
let WellKnownLocalSID = "S-1-5-32-5[0-9][0-9]$";
let WellKnownGroupSID = "S-1-5-21-[0-9]*-[0-9]*-[0-9]*-5[0-9][0-9]$|S-1-5-21-[0-9]*-[0-9]*-[0-9]*-1102$|S-1-5-21-[0-9]*-[0-9]*-[0-9]*-1103$|S-1-5-21-[0-9]*-[0-9]*-[0-9]*-498$|S-1-5-21-[0-9]*-[0-9]*-[0-9]*-1000$";
union isfuzzy=true
(
SecurityEvent
// 4728 - A member was added to a security-enabled global group
// 4732 - A member was added to a security-enabled local group
// 4756 - A member was added to a security-enabled universal group
| where EventID in (4728, 4732, 4756)
| where AccountType == "User"
| where TargetSid matches regex WellKnownLocalSID or TargetSid matches regex WellKnownGroupSID
// Exclude Remote Desktop Users group: S-1-5-32-555
| where TargetSid !in ("S-1-5-32-555")
| extend SimpleMemberName = iff(MemberName == "-", MemberName, substring(MemberName, 3, indexof_regex(MemberName, @",OU|,CN") - 3))
| project TimeGenerated, EventID, Activity, Computer, SimpleMemberName, MemberName, MemberSid, TargetAccount, TargetUserName, TargetDomainName, TargetSid, UserPrincipalName, 
SubjectAccount, SubjectUserName, SubjectDomainName, SubjectUserSid
),
(
WindowsEvent
// 4728 - A member was added to a security-enabled global group
// 4732 - A member was added to a security-enabled local group
// 4756 - A member was added to a security-enabled universal group
| where EventID in (4728, 4732, 4756) and not(EventData has "S-1-5-32-555")
| extend SubjectUserSid = tostring(EventData.SubjectUserSid)
| extend Account =  strcat(tostring(EventData.SubjectDomainName),"\\", tostring(EventData.SubjectUserName))
| extend AccountType=case(Account endswith "$" or SubjectUserSid in ("S-1-5-18", "S-1-5-19", "S-1-5-20"), "Machine", isempty(SubjectUserSid), "", "User")
| extend MemberName = tostring(EventData.MemberName)
| where AccountType == "User"
| extend TargetSid = tostring(EventData.TargetSid)
| where TargetSid matches regex WellKnownLocalSID or TargetSid matches regex WellKnownGroupSID
// Exclude Remote Desktop Users group: S-1-5-32-555
| where TargetSid !in ("S-1-5-32-555")
| extend SimpleMemberName = iff(MemberName == "-", MemberName, substring(MemberName, 3, indexof_regex(MemberName, @",OU|,CN") - 3))
| extend MemberSid = tostring(EventData.MemberSid)
| extend TargetUserName = tostring(EventData.TargetUserName), TargetDomainName = tostring(EventData.TargetDomainName), 
TargetAccount = strcat(tostring(EventData.TargetDomainName),"\\", tostring(EventData.TargetUserName))
| extend UserPrincipalName = tostring(EventData.UserPrincipalName)
| extend SubjectUserName = tostring(EventData.SubjectUserName), SubjectDomainName = tostring(EventData.SubjectDomainName), 
SubjectAccount = strcat(tostring(EventData.SubjectDomainName),"\\", tostring(EventData.SubjectUserName))
| project TimeGenerated, EventID, Computer, SimpleMemberName, MemberName, MemberSid, TargetAccount, TargetUserName, TargetDomainName, TargetSid, UserPrincipalName, 
SubjectAccount, SubjectUserName, SubjectDomainName, SubjectUserSid
)
| extend GroupAddedMemberTo = TargetAccount, AddedByAccount = SubjectAccount, AddedByAccountName = SubjectUserName, AddedByAccountDomainName = SubjectDomainName, 
AddedByAccountSid = SubjectUserSid, AddedMemberName = SimpleMemberName, AddedMemberSid = MemberSid
| extend HostName = tostring(split(Computer, ".")[0]), DomainIndex = toint(indexof(Computer, '.'))
| extend HostNameDomain = iff(DomainIndex != -1, substring(Computer, DomainIndex + 1), Computer)
| project-away DomainIndex

relevantTechniques:
- T1098
- T1078
name: User account added to built in domain local or global group
triggerThreshold: 0
tactics:
- Persistence
- PrivilegeEscalation
severity: Low
id: a35f2c18-1b97-458f-ad26-e033af18eb99
requiredDataConnectors:
- dataTypes:
  - SecurityEvent
  connectorId: SecurityEvents
- dataTypes:
  - SecurityEvent
  connectorId: WindowsSecurityEvents
- dataTypes:
  - WindowsEvent
  connectorId: WindowsForwardedEvents
kind: Scheduled
query: |
  // For AD SID mappings - https://docs.microsoft.com/windows/security/identity-protection/access-control/active-directory-security-groups
  let WellKnownLocalSID = "S-1-5-32-5[0-9][0-9]$";
  let WellKnownGroupSID = "S-1-5-21-[0-9]*-[0-9]*-[0-9]*-5[0-9][0-9]$|S-1-5-21-[0-9]*-[0-9]*-[0-9]*-1102$|S-1-5-21-[0-9]*-[0-9]*-[0-9]*-1103$|S-1-5-21-[0-9]*-[0-9]*-[0-9]*-498$|S-1-5-21-[0-9]*-[0-9]*-[0-9]*-1000$";
  union isfuzzy=true
  (
  SecurityEvent
  // 4728 - A member was added to a security-enabled global group
  // 4732 - A member was added to a security-enabled local group
  // 4756 - A member was added to a security-enabled universal group
  | where EventID in (4728, 4732, 4756)
  | where AccountType == "User"
  | where TargetSid matches regex WellKnownLocalSID or TargetSid matches regex WellKnownGroupSID
  // Exclude Remote Desktop Users group: S-1-5-32-555
  | where TargetSid !in ("S-1-5-32-555")
  | extend SimpleMemberName = iff(MemberName == "-", MemberName, substring(MemberName, 3, indexof_regex(MemberName, @",OU|,CN") - 3))
  | project TimeGenerated, EventID, Activity, Computer, SimpleMemberName, MemberName, MemberSid, TargetAccount, TargetUserName, TargetDomainName, TargetSid, UserPrincipalName, 
  SubjectAccount, SubjectUserName, SubjectDomainName, SubjectUserSid
  ),
  (
  WindowsEvent
  // 4728 - A member was added to a security-enabled global group
  // 4732 - A member was added to a security-enabled local group
  // 4756 - A member was added to a security-enabled universal group
  | where EventID in (4728, 4732, 4756) and not(EventData has "S-1-5-32-555")
  | extend SubjectUserSid = tostring(EventData.SubjectUserSid)
  | extend Account =  strcat(tostring(EventData.SubjectDomainName),"\\", tostring(EventData.SubjectUserName))
  | extend AccountType=case(Account endswith "$" or SubjectUserSid in ("S-1-5-18", "S-1-5-19", "S-1-5-20"), "Machine", isempty(SubjectUserSid), "", "User")
  | extend MemberName = tostring(EventData.MemberName)
  | where AccountType == "User"
  | extend TargetSid = tostring(EventData.TargetSid)
  | where TargetSid matches regex WellKnownLocalSID or TargetSid matches regex WellKnownGroupSID
  // Exclude Remote Desktop Users group: S-1-5-32-555
  | where TargetSid !in ("S-1-5-32-555")
  | extend SimpleMemberName = iff(MemberName == "-", MemberName, substring(MemberName, 3, indexof_regex(MemberName, @",OU|,CN") - 3))
  | extend MemberSid = tostring(EventData.MemberSid)
  | extend TargetUserName = tostring(EventData.TargetUserName), TargetDomainName = tostring(EventData.TargetDomainName), 
  TargetAccount = strcat(tostring(EventData.TargetDomainName),"\\", tostring(EventData.TargetUserName))
  | extend UserPrincipalName = tostring(EventData.UserPrincipalName)
  | extend SubjectUserName = tostring(EventData.SubjectUserName), SubjectDomainName = tostring(EventData.SubjectDomainName), 
  SubjectAccount = strcat(tostring(EventData.SubjectDomainName),"\\", tostring(EventData.SubjectUserName))
  | project TimeGenerated, EventID, Computer, SimpleMemberName, MemberName, MemberSid, TargetAccount, TargetUserName, TargetDomainName, TargetSid, UserPrincipalName, 
  SubjectAccount, SubjectUserName, SubjectDomainName, SubjectUserSid
  )
  | extend GroupAddedMemberTo = TargetAccount, AddedByAccount = SubjectAccount, AddedByAccountName = SubjectUserName, AddedByAccountDomainName = SubjectDomainName, 
  AddedByAccountSid = SubjectUserSid, AddedMemberName = SimpleMemberName, AddedMemberSid = MemberSid
  | extend HostName = tostring(split(Computer, ".")[0]), DomainIndex = toint(indexof(Computer, '.'))
  | extend HostNameDomain = iff(DomainIndex != -1, substring(Computer, DomainIndex + 1), Computer)
  | project-away DomainIndex  
description: |
    'Identifies when a user account has been added to a privileged built in domain local group or global group such as the Enterprise Admins, Cert Publishers or DnsAdmins. Be sure to verify this is an expected addition.'
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Detections/SecurityEvent/UserAccountAddedToPrivlegeGroup_1h.yaml
triggerOperator: gt
queryPeriod: 1d
queryFrequency: 1d
metadata:
  source:
    kind: Community
  categories:
    domains:
    - Security - Others
    - Identity
  author:
    name: Microsoft Security Research
  support:
    tier: Community
version: 1.3.8
entityMappings:
- entityType: Account
  fieldMappings:
  - columnName: SubjectAccount
    identifier: FullName
  - columnName: SubjectUserName
    identifier: Name
  - columnName: SubjectDomainName
    identifier: NTDomain
- entityType: Account
  fieldMappings:
  - columnName: SubjectUserSid
    identifier: Sid
- entityType: Account
  fieldMappings:
  - columnName: AddedMemberName
    identifier: Name
  - columnName: AddedMemberSid
    identifier: Sid
- entityType: Host
  fieldMappings:
  - columnName: Computer
    identifier: FullName
  - columnName: HostName
    identifier: HostName
  - columnName: HostNameDomain
    identifier: NTDomain