Smart App Control Has blocked an app with a dangerous file extension

Files come in many different types—documents, photos, spreadsheets, and apps. Windows identifies what kind of file it is by looking at the file extension, a short set of letters at the end of the file name after a dot.

You’ve likely seen file extensions before. For example, Chemistry paper.docx uses the .DOCX extension, which means it’s a Microsoft Word document. Birthday.jpg uses .JPG, indicating an image file.

Some file extensions, such as .JS or .COM, are used for scripts or executable programs. These files can be useful apps, but they can also be used to deliver malware.

To help protect your device, Smart App Control in the Windows Security app automatically blocks files with certain dangerous file extensions when they’re downloaded from the internet. This reduces the risk of running harmful software on your PC. For a complete list of blocked file extensions, select the heading below.