Windows Defender is included with Windows and helps protect your PC against malware (malicious software). Malware consists of viruses, spyware, and other potentially unwanted software. Malware can infect your PC without your knowledge: it might install itself from an email message, when you connect to the Internet, or when you install certain apps using a USB flash drive, CD, DVD, or other removable media. Some malware can also be programmed to run at unexpected times, not only when it's installed.

Windows Defender helps keep malware from infecting your PC in two ways:

  • Providing real-time protection. Windows Defender notifies you and blocks malware that tries to install itself or run on your PC. It also notifies you when apps try to change important settings.

  • Providing anytime scanning options. Windows Defender automatically scans your PC for installed malware on a regular basis, but you can also start a scan whenever you want. Windows Defender automatically quarantines or removes anything that's detected during a scan. For more info about how to scan your PC using Windows Defender, see How do I find and remove a virus?

When you use Windows Defender, it's important to have up-to-date definitions. Definitions are files that act like an ever-growing encyclopedia of potential software threats. Windows Defender uses definitions to detect any malware and to notify you of potential risks.

To help keep your definitions up to date, Windows Defender checks online for updated definitions before scanning your PC. You can use Windows Update to automatically download and install new definitions as soon as they're released. Learn more about setting up automatic updates.

To open Windows Defender

  • Open Windows Defender by swiping in from the right edge of the screen, and then tapping Search (or if you're using a mouse, pointing to the upper-right corner of the screen, moving the mouse pointer down, and then clicking Search), entering defender in the search box, and then tapping or clicking Windows Defender.


  • If you’re using a PC at work, your IT admin might be using another security program and turn off Windows Defender.

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