Which tool should you employ to receive notifications if deleted SharePoint users downloaded many documents prior to their account deletion?

The appropriate tool for receiving notifications about deleted SharePoint users who downloaded numerous documents prior to account deletion is an insider risk policy. This type of policy is designed to monitor and identify risky behaviors within an organization, including unusual file access or downloads by users who may pose a threat to data security.

Insider risk policies can set parameters to detect actions that are suspicious or indicate potential data exfiltration, such as downloading a large volume of documents shortly before account termination. By leveraging the capabilities of insider risk management, organizations can gain insights into user activity, enabling better risk assessments and proactive measures to mitigate data loss risks.

The other options, while relevant to security and compliance in Office 365, serve different purposes. For example, alert policies in Microsoft Defender for Office 365 are primarily focused on threats from external sources, such as phishing or malware. Access review policies are aimed at assessing user access rights rather than monitoring user behavior related to specific actions like file downloads. Lastly, file policies in Microsoft Defender for Cloud Apps are geared toward controlling and monitoring cloud application usage, not specifically tied to insider actions leading up to account deletions.