Before the release of Windows 8.1, Windows Defender referred to a separate tool that only detected spyware. This tool is no longer supported, as antispyware is included in Microsoft Security Essentials and Windows Defender Antivirus.
Windows Defender is available in earlier versions of Windows 10, but in the most recent versions of Windows 10, Windows Defender is now called Windows Security.
Under Virus & threat protection settings, select Manage settings.
Under Real-time protection, change the setting to On or Off.
For optimal protecion, turn on the settings for Cloud-delivered protection and Automatic sample submission.
Windows Defender Antivirus comes built-in to Windows 10 and Windows 8.1. You can turn off Windows Defender Antivirus if you decide to use a different security product.
Your device will be vulnerable to malware if you disable Windows Defender Antivirus and don’t have another security product.
If you don't have another security product, or it is expired, Windows Defender Antivirus will automatically turn on. You can also enable it manually if you don't already have a security product installed and working.
Generally, you don’t need to do anything as the security software will clean the infection for you.
If unwanted software has been found on your device, you may be asked to choose what to do next. When this happens you will see a message in the bottom corner of your screen, where you can choose to select Clean computer or Show details.
If you choose Clean computer, the file is removed.
The Show details button lets you choose to either remove, quarantine, or allow the file.
Every threat is given an alert level to help you decide what to do.
You can choose to exclude files from scanning if you know they are completely safe.
You should only do this for files you know are absolutely clean—if you are getting repeated warnings about a threat, first you should update your security software, and then check for any other important information about it in the malware encyclopedia.
Be careful—any files that you exclude will not be scanned, which could leave you open to infection. Only exclude files if you are absolutely sure they are not infected.
To exclude a file from scanning:
Open your Microsoft security software.
Go to the Settings tab.
In the Excluded files and locations section, select Browse, find the file you want to exclude, and then select OK.
Select Add, and then select Save changes. You will no longer be alerted about the file.