Entra ID Service Principal with Unusual Source ASN

Description

Identifies Entra ID service principal sign-ins where the workload identity and source autonomous system number (ASN) together have not appeared in recent history. Attackers who obtain application secrets or tokens often authenticate from unfamiliar hosting providers, residential or VPN egress, or networks outside normal automation footprints, which can precede data access, lateral movement, or ransomware activity in the tenant. The detection emphasizes first-seen network context for non-interactive workload identities.

Detection logic

Its licence does not clear it for publishing here

Sunturai publishes a detection's own text where the licence it arrived under has been reviewed and permits it, and Elastic License 2.0 has not. The query as its source wrote it, its canonical form and the hash that pins this revision are in the workspace record.

Detection requirements

Platform: Containers ESXi IaaS Identity Provider Linux macOS Network Devices Office Suite SaaS Windows
The rule states no platform. This is derived from the ATT&CK technique it maps to.
Log source category: event_index

Known benign triggers

Geo-IP and ASN enrichment updates can occasionally shift how a stable egress is labeled, creating a one-time "new" tuple.
New deployments, DR sites, IP rotation, or first-time CI/CD expansion can produce a genuinely new (service principal, ASN) pair without malicious intent. Baseline expected apps and approve new network paths.
Shared or reused service principal secrets across teams may register as new paths when first used from another site.

References

Links the source published beside this detection. Reference is the link the source wrote, unmodified. Class is decided by this catalogue from the host and path, not stated by the source. Cited by counts published detections citing the same resource, including this one, and the sources beneath it count the repositories this catalogue ingests, which is not the same as independent research.
Reference	Class	Cited by
learn.microsoft.com/en-us/entra/identity/conditional-access/workload-identities	Product documentation	Only this detection cites it
learn.microsoft.com/en-us/entra/identity/monitoring-health/concept-sign-ins	Product documentation	6from 2 sources
www.microsoft.com/en-us/security/blog/2025/08/27/storm-0501s-evolving-techniques-lead-to-cloud-based-ransomware/	Threat report	13
www.wiz.io/blog/lateral-movement-risks-in-the-cloud-and-how-to-prevent-them-part-3-from-compromis	Threat report	2

Detection rules

Entra ID Service Principal with Unusual Source ASN

Description

Detection logic

Detection requirements

Known benign triggers

MITRE ATT&CK mappings

References

From the source

Licence

Authorship

Detection rules