Glossary
Microsoft Defender SmartScreen
A reputation service in Windows and Microsoft Edge that warns about or blocks phishing sites, malicious downloads and unknown applications.
Microsoft Defender SmartScreen checks URLs, downloaded files and applications against Microsoft's reputation data. In Microsoft Edge it warns about or blocks known phishing and malware sites and downloads that are malicious or uncommon. In Windows, SmartScreen for apps checks executables carrying the Mark of the Web when a user tries to run them, and shows the "Windows protected your PC" prompt for unknown or unsigned files. Windows 11 22H2 added enhanced phishing protection, which warns when users type their Windows password into a suspicious site or an unsafe application.
SmartScreen stops a large share of commodity phishing and drive-by malware before any other control has to react, but only if users cannot click through its warnings. Enable it by policy for both Windows and Edge, set the Edge policies that prevent bypassing SmartScreen prompts for sites and warnings about downloads, and configure Windows to warn and prevent bypass for apps. Use Defender for Endpoint custom indicators to extend it with your own URL and file blocks.