Describes monthly updates that improve the Windows Defender baseline engines and signatures in Windows 8 or Windows 8.1 OEM disk images.

Provides links to Web sites that describe the Windows Defender definition updates.

Describes the process by which updated anti-malware files are deployed by Microsoft Antivirus Products. This process uses a file-copy operation. This file-copy operation is described here in great detail.

The MpAvBase.vdm file contains the antivirus base definition module. This file is usually updated only one time per month by Microsoft and contains the base virus information that is used to build the delta definitions.

Learn what file name extensions are, which extensions are common in Windows, and how to view them in File Explorer.

With Visio Viewer, you can open, view, or print Visio drawings, even if you don't have Visio installed. You cannot, however, edit, save, or create a new Visio drawing with Visio Viewer. For that, you need a full version of Visio installed.