Office 365 opens files in the sandbox to prevent threats

Microsoft today announced the launch of Guard for Office in a public preview to protect business users from threats that use malicious attachments as a means of attack.

Office Application Protection (also known as Microsoft Defender Application Guard for Office) is designed to prevent files downloaded from unreliable sources from gaining access to trusted resources by opening them in an isolated sandbox.

This sandbox will automatically prevent malicious files from exploiting vulnerabilities, downloading other malicious tools, or any malicious behavior.

Disable by default in supported environments

Office malware is one of the most common files used by hackers to develop malware, such as ransomware, RATs, data theft trojans, and malware downloads.

The Office Application Protection feature works with Word, Excel, PowerPoint, Microsoft 365, and will be disabled by default for clients with Microsoft 365 E5 or Microsoft 365 E5 security software.

In order for administrators to enable it, endpoints are required to run Windows 10 Enterprise Edition, version 2004 (20H1), with the cumulative update KB4566782 and the Application Guard activation package for Office applications installed.

Microsoft Defender ATP integration

"Office Application Protection is a limited feature that isolates unreliable documents from accessing trusted corporate resources, user IDs, and computer files," explains Microsoft.

"As a result, if a user tries to access an unauthorized feature, for example, by importing an image from a local file into the disk, it will fail and a question like the one below will appear.

The Application Guard for Office is integrated with the Microsoft Defender Advanced Threat corporate security platform, providing monitoring of any malicious activity.

Microsoft provides detailed instructions on how to deploy and configure Application Guard for Office.

More details on installing - https://t.co/3V0D1NmoKz

- Tom Gallagher (@secbughunter) August 24