Suspicious Bulk Mail and File Collection via MSGraph Application Access (via m365)

ATT&CK techniques

Cred Access → Collection

Recon
Resource Dev
Initial Access
Execution
Persistence
Priv Esc
Defense Evasion
Cred Access
- T1552Unsecured Credentials
Discovery
Lateral Movement
Collection
- T1114.002Remote Email Collection
C2
Exfiltration
Impact

What it detects

This rule detects application-context access to mailbox items through the Microsoft Graph API by a non-owner identity, the exfiltration behavior Silk Typhoon uses after adding credentials to compromised service principals to steal email and files from targeted tenants. Adversaries prefer app-based MSGraph access to harvest data at scale while evading per-user controls, so bulk MailItemsAccessed events under an application identity indicate cloud data theft.

Reporting behind it

Related detections9 linkedT1552 — drag to rearrange

Suspicious Python Executing Script from var root Library Caches on macOS (via process_creation)

Suspicious Inbox Rule Hiding Mail to Deleted Items via M365 Exchange

Malicious Exchange Mailbox Export to ASPX via New-MailboxExportRequest

Suspicious SCATTERED SPIDER Exchange Transport Rule Creation to Suppress Alerts (via m365)

Malicious SD-WAN Compromise Credential Theft via loot_run.sh

Possible SSRF via VMware Workspace One Access instanceHealth CVE-2021-22056

Suspicious Exchange Online Mail Flow Rule or Connector Creation via Compromised Account

Suspicious Azure Credential Hunting via MicroBurst Modules

Windows Script Interpreter Launching trufflehog or gitleaks Credential Scanner

Suspicious Bulk Mail and File Collection via MSGraph Application Access (via m365)

Pivot detection · T1552 · 9 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 →