Application Guard will block untrusted Office documents

Claudiu Andone
by Claudiu Andone
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  • Defender Application Guard is a security technology designed to sandbox any untrusted files.
  • Microsoft announced that its Defender Application Guard for Office is available now for admins in public preview.
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Defender Application Guard for Office will block untrusted documents

With the last Patch Tuesday event we’ve also seen a record 147 vulnerabilities from which 128 were found in Microsoft products.

So it’s easy to see why the software giant is looking for ways of protecting their products and users.

Probably with this in mind, Microsoft announced that its Defender Application Guard for Office is available for admins in public preview.

What is Defender Application Guard?

Defender Application Guard is a security technology that works like a big sandbox by isolating untrusted Office documents and analyzing them before they reach the operating system and do any damage.

A blog post in Microsoft’s Tech Comunity blog explains how the Defender Application Guard works:

Microsoft Office will open files from potentially unsafe locations in  Microsoft Defender Application Guard, a secure container, that is isolated from the device through hardware-based virtualization.

When Microsoft Office opens files in Microsoft Defender Application Guarda user can then securely read, edit,  print, and save the files without having to re-open files outside of the container.

Application Guard is not a new technology but it was introduced in 2018 and was designed for Microsoft Edge, the old HTML version.

And the technology back then had even bolder action because it created virtualized versions of Windows and Edge using the HyperVisor technology.

That was a way to create a safe browsing environment without getting your real instances of your OS and browser exposed to any threats. And when you would finish the session, the virtual instanced would have been discarded.

How does the Application Guard for Office work?

The Application Guard for Office does a similar action for office documents from Word, Excel, or PowerPoint. Not the ones you create on your computer but the ones that you download from the Internet or any other potentially untrusted sources.

For instance, if you want to open a Word document you just received in your Outlook, the file will start in an Application Guard sandbox that will prevent potentially harmful code from spreading on your PC.

The technology seems great but the minimum hardware requirements specified by Microsoft are pretty high:

  • CPU: 64-bit, 4 cores (physical or virtual), virtualization extensions (Intel VT-x OR AMD-V), Core i5 equivalent or higher recommended
  • Physical memory: 8-GB RAM
  • Hard disk: 10 GB of free space on the system drive (SSD recommended)

What do you think about Application Guard for Office? Write your opinion in our Comments section below.