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SmartScreen Prevented Unrecognized App — Windows Defender SmartScreen Block

Warningsecurity

Overview

Fix Windows Defender SmartScreen blocking an application from starting with the 'Windows protected your PC' warning for unrecognized or unsigned programs.

Key Details

  • SmartScreen checks downloaded executables against Microsoft's reputation database
  • Applications without a valid code signing certificate or without established reputation are flagged
  • The blue 'Windows protected your PC' screen prevents the application from running by default
  • SmartScreen also checks URLs in Edge and Microsoft Store apps for known malicious content
  • New legitimate software often gets flagged until it builds reputation through sufficient downloads

Common Causes

  • Application is not digitally signed with a code signing certificate
  • Application is newly released and has not built up reputation in Microsoft's database
  • Application downloaded from the internet has a Mark of the Web (MOTW) zone identifier
  • Software actually contains malware or potentially unwanted software (PUP)

Steps

  1. 1Click 'More info' on the SmartScreen warning, then click 'Run anyway' if you trust the source
  2. 2Right-click the downloaded file > Properties > check 'Unblock' at the bottom to remove MOTW
  3. 3Scan the file with Windows Defender or VirusTotal.com before running unrecognized software
  4. 4For developers: code sign your application with a trusted certificate to prevent SmartScreen warnings
  5. 5For IT admins: configure SmartScreen via Group Policy rather than disabling it system-wide

Tags

smartscreenwindows-defenderblocked-appsecuritycode-signing

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Frequently Asked Questions

No. SmartScreen provides important protection against malware. Instead, use 'Run anyway' for specific trusted applications. Disabling SmartScreen removes a critical security layer for all downloads.