Microsoft 365 Cloud App Security: Unusual Large Volume of File Deletion

Alerts when Microsoft 365 threat telemetry shows a user successfully deleting an unusually large number of files.

FreeReviewedSigma · Medium · v4

Product: m365
Service: threat_management
Author: austinsonger (SigmaHQ), DRL 1.1
Published: 2021-08-19
Updated: 2026-07-31

ATT&CK techniques

Impact

Recon
Resource Dev
Initial Access
Execution
Persistence
Priv Esc
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact
- T1485Data Destruction

What it detects

This rule flags cases where Microsoft Cloud App Security reports a successful event indicating a user deleted an unusually large volume of files. Attackers may attempt to disrupt services or destroy data, and high-volume deletions are a common impact pattern worth investigating. The detection relies on threat management telemetry from Microsoft 365 identifying the specific event source, event name, and successful status.

Reporting behind it

Related detections9 linkedT1485 — drag to rearrange

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Malicious DYNOWIPER PowerShell Loader Execution (via ps_script)

Suspicious S3 Lifecycle Policy Set for Rapid Object Deletion

Malicious PathWiper Loader Script Execution from Windows Temp via WScript

Suspicious Free Space Wipe via cipher.exe

Suspicious sha256sum.exe Execution from Windows Temp Directory

Suspicious Secure Deletion of Free Space via Cipher (via process_creation)

Microsoft 365 Cloud App Security: Unusual Large Volume of File Deletion

Pivot detection · T1485 · 9 related

Changelog

v4
Candidate ingested via manual entry.2026-07-31
v3
Candidate ingested via manual entry.2026-07-31
v2
Candidate ingested via manual entry.2026-07-31
v1
No changelog recorded for this version.2026-07-30

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

microsoft-365-threat-management-high-volume-file-deletion-by-a-user-78a34b67

title: "Microsoft 365 Cloud App Security: Unusual Large Volume of File Deletion"
id: c144460f-42da-4f07-8f15-a43afff380f1
status: test
description: This rule flags cases where Microsoft Cloud App Security reports a successful event indicating a user deleted an unusually large volume of files. Attackers may attempt to disrupt services or destroy data, and high-volume deletions are a common impact pattern worth investigating. The detection relies on threat management telemetry from Microsoft 365 identifying the specific event source, event name, and successful status.
references:
  - https://learn.microsoft.com/en-us/defender-cloud-apps/anomaly-detection-policy
  - https://learn.microsoft.com/en-us/defender-cloud-apps/policy-template-reference
  - https://github.com/SigmaHQ/sigma/blob/master/rules/cloud/m365/threat_management/microsoft365_unusual_volume_of_file_deletion.yml
author: austinsonger, Huntrule Team
date: 2021-08-19
modified: 2022-10-09
tags:
  - attack.impact
  - attack.t1485
logsource:
  service: threat_management
  product: m365
detection:
  selection:
    eventSource: SecurityComplianceCenter
    eventName: Unusual volume of file deletion
    status: success
  condition: selection
falsepositives:
  - Unknown
level: medium
license: DRL-1.1
related:
  - id: 78a34b67-3c39-4886-8fb4-61c46dc18ecd
    type: derived

Convert

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