If you want Windows to update your software, go to Windows Update or: Because these updates change once a day, the definition version might be different to what is shown on this page, even after you've clicked the Update button.
This page explains how updates work and where to get them.
If you don't already have Microsoft security software, or you want to reinstall it, see our software download page.
If you're using Windows XP, see our Windows XP end of support page.
For a list of the latest updates see the change log.
For antimalware and antispyware, the latest definitions are End of life for Microsoft Forefront Client Security was on July 14th 2015.
Customers are encouraged to migrate to System Center Endpoint Protection.For more information see the Forefront Client Security entry at the Microsoft Support Lifecycle site.Windows will automatically download and install updates once a day for you.If automatic updates aren't working there might be an issue with your PC: You can also force a download of the latest daily update.This is the same as when Windows automatically downloads the update, and can be useful if you aren't always connected to the Internet or haven't turned your PC on for a few days.If you want a more recent update (usually uploaded to this page within the last three hours), you can manually download and install it.