Suspicious Microsoft Teams Message from External Tenant Impersonating Helpdesk

ATT&CK techniques

Initial Access

Recon
Resource Dev
Initial Access
- T1566.003Spearphishing via Service
Execution
Persistence
Priv Esc
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule detects one-on-one Microsoft Teams chat messages originating from external tenants where the sender identity references helpdesk, IT, or support, matching the helpdesk impersonation vishing technique tracked by eSentire. Attackers pose as internal support over federated Teams to socially engineer users into granting access, so external senders using these identities are a phishing indicator.

Reporting behind it

Related detections5 linkedT1684.001 — drag to rearrange

Suspicious ClickFix PowerShell Execution with Hidden Window (via process_creation)

Suspicious Contagious Interview Disk Enumeration via Node Spawning Wmic

Suspicious Spoofed Inbound Email With Failed Authentication and Anonymous Internal Sender (via m365)

Suspicious Error 524 Decoy Smishing Phishing Endpoint Access (via proxy)

Suspicious 0ktapus Phishing Kit Credential Post Path Access

Suspicious Microsoft Teams Message from External Tenant Impersonating Helpdesk

Pivot detection · T1684.001 · 5 related

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.

Full detection rule

Unlock this rule to view and copy it

The detection logic is included with a plan. Everything else — context, mappings and implementation details — stays free on this page.

Sign in for 3 free unlocks

Signing in gives you 3 unlocks to spend on any rule in the library. No card, and they do not expire.

Also included

Unlocked rules convert on this page — to Splunk SPL or Splunk — Raw Index SPL or Microsoft Sentinel KQL or Microsoft Sentinel ASIM ASIM KQL or Microsoft Defender XDR KQL or Elastic Security KQL or Elastic Security Lucene or Elastic Security ES|QL or CrowdStrike Falcon CQL or SentinelOne PowerQuery or Palo Alto Cortex XDR XQL or Carbon Black Cloud Platform Search or Carbon Black EDR Process Search or Google Security Operations UDM Search or IBM QRadar AQL or Sumo Logic Cloud SIEM Rules expression or Rapid7 InsightIDR LEQL or Graylog Search or OpenSearch Lucene or OpenSearch PPL PPL or Grafana Loki LogQL or SQLite SQL or Zircolite SQLite — with the log-source profile the engine picked, the field map it used, and everything it could not express. Converting a rule you have unlocked costs no further credit.

See it run on a free rule →Convert your own rule →