Silk Typhoon New UM Service Child Process

Severity: medium
Time window: 14d
Author: Microsoft Security Research
Source: github.com/Azure/Azure-Sentinel

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/

MITRE ATT&CK coverage

Tactic	Techniques
Initial Access	`T1190` Exploit Public-Facing Application

Event coverage

Provider	Event	Title
Security-Auditing	Event ID 4688	A new process has been created.

Rule body kusto

id: 95a15f39-d9cc-4667-8cdd-58f3113691c9
name: 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
requiredDataConnectors:
  - connectorId: SecurityEvents
    dataTypes:
      - SecurityEvent
  - connectorId: WindowsSecurityEvents
    dataTypes:
      - SecurityEvent
  - connectorId: WindowsSecurityEvents
    dataTypes: 
      - SecurityEvents 
  - connectorId: WindowsForwardedEvents
    dataTypes: 
      - WindowsEvent 
queryFrequency: 1d
queryPeriod: 14d
triggerOperator: gt
triggerThreshold: 0
tactics:
  - InitialAccess
relevantTechniques:
  - T1190
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
  ))  
entityMappings:
  - entityType: Account
    fieldMappings:
      - identifier: FullName
        columnName: SubjectAccount
      - identifier: Name
        columnName: SubjectUserName
      - identifier: NTDomain
        columnName: SubjectDomainName
  - entityType: Host
    fieldMappings:
      - identifier: FullName
        columnName: Computer
      - identifier: HostName
        columnName: HostName
      - identifier: NTDomain
        columnName: HostNameDomain
  - entityType: IP
    fieldMappings:
      - identifier: Address
        columnName: IpAddress
version: 1.1.5
kind: Scheduled
metadata:
    source:
        kind: Community
    author:
        name: Microsoft Security Research
    support:
        tier: Community
    categories:
        domains: [ "Security - Threat Intelligence" ]

Stages and Predicates

Stage 0: `let`

let lookback = 14d;
let timeframe = 1d;

Stage 1: `union`

union isfuzzy=true

Stage 2: `source`

SecurityEvent

Stage 3: `where` time_window=1209600s

| where TimeGenerated > ago(lookback) and TimeGenerated < ago(timeframe)

Stage 4: `where`

| where EventID == 4688

Stage 5: `where`

| where ParentProcessName has_any ("umworkerprocess.exe", "UMService.exe")

Stage 6: `join`

| join kind=rightanti (
SecurityEvent
| where TimeGenerated > ago(timeframe)
| where ParentProcessName has_any ("umworkerprocess.exe", "UMService.exe")
| where EventID == 4688) on NewProcessName

Stage 7: `source`

WindowsEvent

Stage 8: `where` time_window=1209600s

| where TimeGenerated > ago(lookback) and TimeGenerated < ago(timeframe)

Stage 9: `where`

| where EventID == 4688 and EventData has_any ("umworkerprocess.exe", "UMService.exe")

Stage 10: `extend`

| extend ParentProcessName = tostring(EventData.ParentProcessName)

Stage 11: `where`

| where ParentProcessName has_any ("umworkerprocess.exe", "UMService.exe")

Stage 12: `extend`

| extend NewProcessName = tostring(EventData.NewProcessName)

Stage 13: `extend`

| extend Account = strcat(tostring(EventData.SubjectDomainName),"\\", tostring(EventData.SubjectUserName))

Stage 14: `extend`

| extend IpAddress = tostring(EventData.IpAddress)

Stage 15: `join`

| 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

Stage 16: `extend`

| extend HostName = tostring(split(Computer, ".")[0]), DomainIndex = toint(indexof(Computer, '.'))

Stage 17: `extend`

| extend HostNameDomain = iff(DomainIndex != -1, substring(Computer, DomainIndex + 1), Computer)

Stage 18: `extend`

| extend SubjectUserName = tostring(EventData.SubjectUserName), SubjectDomainName = tostring(EventData.SubjectDomainName)

Stage 19: `project-away`

| project-away DomainIndex

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
`EventData`	match	`UMService.exe` `umworkerprocess.exe`
`EventID`	eq	`4688` transforms: `cased` corpus 312 (splunk 283, kusto 29)
`ParentProcessName`	match	`UMService.exe` `umworkerprocess.exe`

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
`ParentProcessName`	`extend`
`NewProcessName`	`extend`
`Account`	`extend`
`IpAddress`	`extend`
`HostName`	`extend`
`HostNameDomain`	`extend`
`SubjectDomainName`	`extend`
`SubjectUserName`	`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:`)
`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)

Silk Typhoon New UM Service Child Process

MITRE ATT&CK coverage

Event coverage

Rule body kusto

Stages and Predicates

Stage 0: `let`

Stage 1: `union`

Stage 2: `source`

Stage 3: `where` time_window=1209600s

Stage 4: `where`

Stage 5: `where`

Stage 6: `join`

Stage 7: `source`

Stage 8: `where` time_window=1209600s

Stage 9: `where`

Stage 10: `extend`

Stage 11: `where`

Stage 12: `extend`

Stage 13: `extend`

Stage 14: `extend`

Stage 15: `join`

Stage 16: `extend`

Stage 17: `extend`

Stage 18: `extend`

Stage 19: `project-away`

Indicators

Output fields

Keyboard shortcuts

Search operators

Silk Typhoon New UM Service Child Process

MITRE ATT&CK coverage

Event coverage

Rule body kusto

Stages and Predicates

Stage 0: let

Stage 1: union

Stage 2: source

Stage 3: where time_window=1209600s

Stage 4: where

Stage 5: where

Stage 6: join

Stage 7: source

Stage 8: where time_window=1209600s

Stage 9: where

Stage 10: extend

Stage 11: where

Stage 12: extend

Stage 13: extend

Stage 14: extend

Stage 15: join

Stage 16: extend

Stage 17: extend

Stage 18: extend

Stage 19: project-away

Indicators

Output fields

Stage 0: `let`

Stage 1: `union`

Stage 2: `source`

Stage 3: `where` time_window=1209600s

Stage 4: `where`

Stage 5: `where`

Stage 6: `join`

Stage 7: `source`

Stage 8: `where` time_window=1209600s

Stage 9: `where`

Stage 10: `extend`

Stage 11: `where`

Stage 12: `extend`

Stage 13: `extend`

Stage 14: `extend`

Stage 15: `join`

Stage 16: `extend`

Stage 17: `extend`

Stage 18: `extend`

Stage 19: `project-away`