Silk Typhoon New UM Service Child Process

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Id	95a15f39-d9cc-4667-8cdd-58f3113691c9
Rulename	Silk Typhoon New UM Service Child Process
Description	This query looks for new processes being spawned by the Exchange UM service where that process has not previously been observed before. Reference: https://www.microsoft.com/security/blog/2021/03/02/hafnium-targeting-exchange-servers/
Severity	Medium
Tactics	InitialAccess
Techniques	T1190
Required data connectors	SecurityEvents WindowsForwardedEvents WindowsSecurityEvents
Kind	Scheduled
Query frequency	1d
Query period	14d
Trigger threshold	0
Trigger operator	gt
Source Uri	https://github.com/Azure/Azure-Sentinel/blob/master/Detections/SecurityEvent/SilkTyphoonNewUMServiceChildProcess.yaml
Version	1.1.5
Arm template	95a15f39-d9cc-4667-8cdd-58f3113691c9.json

KQL

let lookback = 14d;
let timeframe = 1d;
(union isfuzzy=true
(SecurityEvent
| where TimeGenerated > ago(lookback) and TimeGenerated < ago(timeframe)
| where EventID == 4688
| where ParentProcessName has_any ("umworkerprocess.exe", "UMService.exe")
| join kind=rightanti (
SecurityEvent
| where TimeGenerated > ago(timeframe)
| where ParentProcessName has_any ("umworkerprocess.exe", "UMService.exe")
| where EventID == 4688) on NewProcessName
),
(WindowsEvent
| where TimeGenerated > ago(lookback) and TimeGenerated < ago(timeframe)
| where EventID == 4688 and EventData has_any ("umworkerprocess.exe", "UMService.exe")
| extend ParentProcessName = tostring(EventData.ParentProcessName)
| where ParentProcessName has_any ("umworkerprocess.exe", "UMService.exe")
| extend NewProcessName = tostring(EventData.NewProcessName)
| extend Account = strcat(tostring(EventData.SubjectDomainName),"\\", tostring(EventData.SubjectUserName))
| extend IpAddress = tostring(EventData.IpAddress)
| join kind=rightanti (
WindowsEvent
| where TimeGenerated > ago(timeframe)
| where EventID == 4688  and EventData has_any ("umworkerprocess.exe", "UMService.exe")
| extend ParentProcessName = tostring(EventData.ParentProcessName)
| where ParentProcessName has_any ("umworkerprocess.exe", "UMService.exe")
| extend NewProcessName = tostring(EventData.NewProcessName)
| extend Account = strcat(tostring(EventData.SubjectDomainName),"\\", tostring(EventData.SubjectUserName))
| extend IpAddress = tostring(EventData.IpAddress)) on NewProcessName
| extend HostName = tostring(split(Computer, ".")[0]), DomainIndex = toint(indexof(Computer, '.'))
| extend HostNameDomain = iff(DomainIndex != -1, substring(Computer, DomainIndex + 1), Computer)
| extend SubjectUserName = tostring(EventData.SubjectUserName), SubjectDomainName = tostring(EventData.SubjectDomainName)
| project-away DomainIndex
))

YAML

entityMappings:
- fieldMappings:
  - columnName: SubjectAccount
    identifier: FullName
  - columnName: SubjectUserName
    identifier: Name
  - columnName: SubjectDomainName
    identifier: NTDomain
  entityType: Account
- fieldMappings:
  - columnName: Computer
    identifier: FullName
  - columnName: HostName
    identifier: HostName
  - columnName: HostNameDomain
    identifier: NTDomain
  entityType: Host
- fieldMappings:
  - columnName: IpAddress
    identifier: Address
  entityType: IP
severity: Medium
name: Silk Typhoon New UM Service Child Process
triggerThreshold: 0
triggerOperator: gt
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Detections/SecurityEvent/SilkTyphoonNewUMServiceChildProcess.yaml
id: 95a15f39-d9cc-4667-8cdd-58f3113691c9
kind: Scheduled
queryFrequency: 1d
relevantTechniques:
- T1190
description: |
  'This query looks for new processes being spawned by the Exchange UM service where that process has not previously been observed before. 
  Reference: https://www.microsoft.com/security/blog/2021/03/02/hafnium-targeting-exchange-servers/'  
query: |
  let lookback = 14d;
  let timeframe = 1d;
  (union isfuzzy=true
  (SecurityEvent
  | where TimeGenerated > ago(lookback) and TimeGenerated < ago(timeframe)
  | where EventID == 4688
  | where ParentProcessName has_any ("umworkerprocess.exe", "UMService.exe")
  | join kind=rightanti (
  SecurityEvent
  | where TimeGenerated > ago(timeframe)
  | where ParentProcessName has_any ("umworkerprocess.exe", "UMService.exe")
  | where EventID == 4688) on NewProcessName
  ),
  (WindowsEvent
  | where TimeGenerated > ago(lookback) and TimeGenerated < ago(timeframe)
  | where EventID == 4688 and EventData has_any ("umworkerprocess.exe", "UMService.exe")
  | extend ParentProcessName = tostring(EventData.ParentProcessName)
  | where ParentProcessName has_any ("umworkerprocess.exe", "UMService.exe")
  | extend NewProcessName = tostring(EventData.NewProcessName)
  | extend Account = strcat(tostring(EventData.SubjectDomainName),"\\", tostring(EventData.SubjectUserName))
  | extend IpAddress = tostring(EventData.IpAddress)
  | join kind=rightanti (
  WindowsEvent
  | where TimeGenerated > ago(timeframe)
  | where EventID == 4688  and EventData has_any ("umworkerprocess.exe", "UMService.exe")
  | extend ParentProcessName = tostring(EventData.ParentProcessName)
  | where ParentProcessName has_any ("umworkerprocess.exe", "UMService.exe")
  | extend NewProcessName = tostring(EventData.NewProcessName)
  | extend Account = strcat(tostring(EventData.SubjectDomainName),"\\", tostring(EventData.SubjectUserName))
  | extend IpAddress = tostring(EventData.IpAddress)) on NewProcessName
  | extend HostName = tostring(split(Computer, ".")[0]), DomainIndex = toint(indexof(Computer, '.'))
  | extend HostNameDomain = iff(DomainIndex != -1, substring(Computer, DomainIndex + 1), Computer)
  | extend SubjectUserName = tostring(EventData.SubjectUserName), SubjectDomainName = tostring(EventData.SubjectDomainName)
  | project-away DomainIndex
  ))    
version: 1.1.5
tactics:
- InitialAccess
queryPeriod: 14d
metadata:
  source:
    kind: Community
  support:
    tier: Community
  author:
    name: Microsoft Security Research
  categories:
    domains:
    - Security - Threat Intelligence
requiredDataConnectors:
- dataTypes:
  - SecurityEvent
  connectorId: SecurityEvents
- dataTypes:
  - SecurityEvent
  connectorId: WindowsSecurityEvents
- dataTypes:
  - SecurityEvents
  connectorId: WindowsSecurityEvents
- dataTypes:
  - WindowsEvent
  connectorId: WindowsForwardedEvents

ARM