↳ GitHub sourceAnalytics ruleLow
Silk Typhoon Suspicious UM Service Error
Description
'This query looks for errors that may indicate that an attacker is attempting to exploit a vulnerability in the service.
Reference: https://www.microsoft.com/security/blog/2021/03/02/hafnium-targeting-exchange-servers/'
- Rule type
- Scheduled
- Version
- 1.0.4
- Query frequency
- 1d
- Query period
- 1d
- Trigger
- gt 0
Declared MITRE coverage
KQL query
Original query, unchanged.
Event
| where EventLog =~ "Application"
| where Source startswith "MSExchange"
| where EventLevelName =~ "error"
| where (RenderedDescription startswith "Watson report" and RenderedDescription contains "umworkerprocess" and RenderedDescription contains "TextFormattingRunProperties") or RenderedDescription startswith "An unhandled exception occurred in a UM worker process" or RenderedDescription startswith "The Microsoft Exchange Unified Messaging service" or RenderedDescription contains "MSExchange Unified Messaging"
| where RenderedDescription !contains "System.OutOfMemoryException"
| extend HostName = tostring(split(Computer, ".")[0]), DomainIndex = toint(indexof(Computer, '.'))
| extend HostNameDomain = iff(DomainIndex != -1, substring(Computer, DomainIndex + 1), Computer)
| project-away DomainIndex
Declared entities
Source provenance
GitHubDisplayed values come from files in Azure/Azure-Sentinel. They describe the published template, not your workspace configuration.
- Commit
629d1d3↗- Source identifier
0625fcce-6d52-491e-8c68-1d9b801d25b9
Additional source files 1
Detections/SecurityEvent/SilkTyphoonSuspiciousUMServiceError.yamlsource ↗GSTEP / CATALOG TRACKING
Added to catalog : 16 Sept 2026 · 05:49 UTC
Last change observed : 16 Sept 2026 · 05:49 UTC