Microsoft 365 mass download
A burst of SharePoint / OneDrive file downloads or a full sync from one account in a short window — the shape of bulk collection / exfiltration after…
What it detects
A burst of SharePoint / OneDrive file downloads or a full sync from one account in a short window — the shape of bulk collection / exfiltration after account takeover, where an attacker pulls a mailbox owner's document library wholesale.
MITRE ATT&CK mapping
False positives and triage
Onboarding a new device or a legitimate bulk export also downloads many files. The signal is a large burst from an unfamiliar client IP, outside business hours, or correlated with a suspicious sign-in / new inbox rule.
The rule
Declarative YAML read by the detection engine — data, never executed. Confidence 60%. Source: rules/cloud/m365_mass_download.yaml, licensed under the Apache License 2.0.
id: cloud.identity.m365_mass_download
version: 1.0.0
status: stable
severity: medium
confidence: 0.6
platforms: [application]
mitre_techniques: [T1213.002, T1530]
description: |
A burst of SharePoint / OneDrive file downloads or a full sync from one account
in a short window — the shape of bulk collection / exfiltration after account
takeover, where an attacker pulls a mailbox owner's document library wholesale.
match:
provider: Office365
event_action_any:
- FileDownloaded
- FileSyncDownloadedFull
- FileSyncDownloadedPartial
threshold:
count: 50
window_seconds: 600
group_by: [user_name]
correlation_keys: [user_name]
false_positive_guidance: |
Onboarding a new device or a legitimate bulk export also downloads many files.
The signal is a large burst from an unfamiliar client IP, outside business
hours, or correlated with a suspicious sign-in / new inbox rule.
Related detections
Run this rule on your own logs — offline
KIROSEC runs this rule and the rest of the library over Windows, Linux, macOS and cloud audit logs on the analyst's own machine. Every alert links to the events that raised it, and nothing leaves the device.