When it comes to removing spyware from your computer, it can be imperative to have the latest definitions files in order to remove the nasty files from you machine. Automatic scanning in Windows Defender, by default, does not check for the latest definitions file prior to scanning your system. To enable the automatic retrieval of the definition file prior to performing the Auto scanning, follow these steps:
1. Open Windows Defender.
2. Click Tools.
3. Under Settings, select Options.
4. In the Automatic scanning section, check the Check for updated definitions before scanning checkbox.
5. Click the Save button.
Windows Defender will now check for updates to the Detection Database and download the new definitions file prior to scanning.