Fake computer account created

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Id	c1faf5e8-6958-11ec-90d6-0242ac120003
Rulename	Fake computer account created
Description	This query detects domain user accounts creation (event ID 4720) where the username ends with $. Accounts that end with $ are normally domain computer accounts and when they are created the event ID 4741 is generated instead. Ref: https://blog.menasec.net/2019/02/threat-hunting-6-hiding-in-plain-sights.html
Severity	Medium
Tactics	DefenseEvasion
Techniques	T1564
Required data connectors	SecurityEvents
Kind	Scheduled
Query frequency	1h
Query period	1h
Trigger threshold	0
Trigger operator	gt
Source Uri	https://github.com/Azure/Azure-Sentinel/blob/master/Detections/SecurityEvent/FakeComputerAccountCreated.yaml
Version	1.0.3
Arm template	c1faf5e8-6958-11ec-90d6-0242ac120003.json

KQL

SecurityEvent
| where EventID == 4720 and TargetUserName endswith "$"
| summarize StartTime = min(TimeGenerated), EndTime = max(TimeGenerated) by Computer, SubjectUserName, SubjectDomainName, SubjectAccount, SubjectUserSid, SubjectLogonId, 
TargetUserName, TargetDomainName, TargetAccount, TargetSid, UserPrincipalName
| extend HostName = tostring(split(Computer, ".")[0]), DomainIndex = toint(indexof(Computer, '.'))
| extend HostNameDomain = iff(DomainIndex != -1, substring(Computer, DomainIndex + 1), Computer)
| project-away DomainIndex

YAML

tactics:
- DefenseEvasion
description: |
  'This query detects domain user accounts creation (event ID 4720) where the username ends with $. 
  Accounts that end with $ are normally domain computer accounts and when they are created the event ID 4741 is generated instead.
  Ref: https://blog.menasec.net/2019/02/threat-hunting-6-hiding-in-plain-sights.html'  
entityMappings:
- entityType: Account
  fieldMappings:
  - identifier: FullName
    columnName: SubjectAccount
  - identifier: Name
    columnName: SubjectUserName
  - identifier: NTDomain
    columnName: SubjectDomainName
- entityType: Account
  fieldMappings:
  - identifier: Sid
    columnName: SubjectUserSid
- entityType: Account
  fieldMappings:
  - identifier: FullName
    columnName: TargetAccount
  - identifier: Name
    columnName: TargetUserName
  - identifier: NTDomain
    columnName: TargetDomainName
- entityType: Account
  fieldMappings:
  - identifier: Sid
    columnName: TargetSid
- entityType: Host
  fieldMappings:
  - identifier: FullName
    columnName: Computer
  - identifier: HostName
    columnName: HostName
  - identifier: DnsDomain
    columnName: HostNameDomain
triggerThreshold: 0
query: |
  SecurityEvent
  | where EventID == 4720 and TargetUserName endswith "$"
  | summarize StartTime = min(TimeGenerated), EndTime = max(TimeGenerated) by Computer, SubjectUserName, SubjectDomainName, SubjectAccount, SubjectUserSid, SubjectLogonId, 
  TargetUserName, TargetDomainName, TargetAccount, TargetSid, UserPrincipalName
  | extend HostName = tostring(split(Computer, ".")[0]), DomainIndex = toint(indexof(Computer, '.'))
  | extend HostNameDomain = iff(DomainIndex != -1, substring(Computer, DomainIndex + 1), Computer)
  | project-away DomainIndex  
version: 1.0.3
metadata:
  source:
    kind: Community
  support:
    tier: Community
  author:
    name: Vasileios Paschalidis
  categories:
    domains:
    - Security - Others
requiredDataConnectors:
- connectorId: SecurityEvents
  dataTypes:
  - SecurityEvent
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Detections/SecurityEvent/FakeComputerAccountCreated.yaml
queryFrequency: 1h
queryPeriod: 1h
severity: Medium
name: Fake computer account created
triggerOperator: gt
id: c1faf5e8-6958-11ec-90d6-0242ac120003
kind: Scheduled
relevantTechniques:
- T1564

ARM