Microsoft Purview compliance portal: Data Loss Prevention – Detection of True file type in EXO DLP

Originally posted by Microsoft May 12, 2025 Uncategorized 0 Comments

Traditionally, Exchange has relied solely on the file extension (e.g., .docx, .pdf) to identify the type of an attachment. However, this approach can be bypassed if a file is renamed with a misleading extension. To address this, we’re enhancing our detection logic to go beyond just the visible file extension.

With this update, even if a file’s extension is altered, Exchange will evaluate the actual content of the file to determine its true type. This ensures that policies based on file type—such as “File extension is…”—remain effective and secure, even in cases of renamed or disguised attachments.

This improvement provides customers with a more robust and reliable way to enforce compliance and security rules around file sharing.

Product
Release phase	Preview
Release date	August CY2025 Preview date: July CY2025
Platform	Web
Cloud Instance	Worldwide (Standard Multi-Tenant), GCC, GCC High
Created	2025-05-09
Roadmap ID	493291
Roadmap Link	https://www.microsoft.com/microsoft-365/roadmap?id=493291