Windows Defender and Windows SmartScreen fight viruses and other malware

By | December 17, 2013

Windows Defender and Windows SmartScreen are built into Windows 8 and Windows RT and help guard your PC against viruses, spyware, and other malicious software in real time. Windows Defender uses green, yellow, and red color codes to show your PC’s security status.

The Home tab in Windows Defender, showing a protected PC
If there’s a red or yellow threat, Windows Defender notifies you and recommends what to do.

When Windows Defender detects a suspicious app or other unfamiliar software, it checks it against a Microsoft database to make sure it isn’t known to do anything potentially harmful. Windows Defender keeps track of known malware automatically, but you can also get updated lists whenever you want.

The Update tab in Windows Defender
These definitions are updated automatically, and whenever you tap or click Update.

Windows Defender runs in the background, and only notifies you if there are specific actions to take—but you can also run your own scan whenever you want. If your PC isn’t working properly, or you got an email from someone you know that just doesn’t seem right, use Windows Defender to check for malware you might have downloaded inadvertently.


  • In Windows 8 and Windows RT, Windows Defender provides the same level of protection against malware as Microsoft Security Essentials. You can’t use Microsoft Security Essentials with Windows 8 or Windows RT, but you don’t need to—Windows Defender is already included and ready to go.

Windows SmartScreen is a new safety feature in Windows 8 and Windows RT that can help protect you from new malware that antimalware software hasn’t detected yet. When you download and run an app downloaded from the Internet, SmartScreen uses information about the app’s reputation to warn you if the app isn’t well-known and might be malicious.

Windows SmartScreen warning dialog
Running unrecognized apps might put your PC or your personal information at risk

SmartScreen Filter in Internet Explorer helps protect users from phishing and malware attacks by warning you if a website or download location has been reported as unsafe.

SmartScreen Filter warning in Internet Explorer
You’ll see a warning like this if you browse to an unsafe website

Scan your PC with Windows Defender

Here’s how:

  • From the Search charm, search for defender and then open Windows Defender.
  • On the Home tab, choose a scan option and then tap or click Scan now.

Choosing what to scan

There are several ways to scan only certain files, drives, or processes with Windows Defender. Not scanning everything on your PC can help speed up a Windows Defender scan, but it can also leave your PC vulnerable to threats in the areas you didn’t check.

  1. From the Search charm, search for defender and then open Windows Defender.
  2. Select Custom, and then tap or click Scan now.

Select the check box for each file and folder you want to scan, and then tap or click OK.

The Windows Defender dialog box of drives and folders
A custom scan lets you choose which drives and folders to scan.
If you want Windows Defender to always skip a particular file, a type of file, or a process on your PC (such as an app that you’re sure isn’t malware), you can change your Windows Defender settings to ignore some items even when it’s running in the background. You should be especially careful excluding anything from regular scans, though—you want to be really sure. Here’s how:
  1. From the Search charm, search for defender and then open Windows Defender.
  2. On the Settings tab, do one or more of the following:
    • Choose Excluded files and locations to add items you don’t want Windows Defender to scan.
    • Choose Excluded file types to add file extensions (such as .bmp or .doc) for file types you don’t want Windows Defender to scan.
    • Choose Excluded processes to add file extensions (such as .exe or .com) for processes that run on your PC that you don’t want Windows Defender to scan.
  3. When you’re finished excluding items, tap or click Save changes. Administrator permission required You might be asked for an admin password or to confirm your choice.
    The Excluded files and locations page on the Settings tab in Windows Defender

    Windows Defender found something! What do I do?

    In addition to the color codes for your PC’s overall security status, Windows Defender applies an alert level to any suspected malware it detects. You can decide whether to remove an item entirely, research it further, or let it run because you recognize it.

    Adjust Windows SmartScreen settings

    You can adjust SmartScreen settings in Action Center. Here’s how:

    1. From the Search charm, search for Action Center and then open Action Center.
    2. Tap or click Change Windows SmartScreen settings.
    Windows SmartScreen settings dialog