Windows Defender is Anti-Malware software build into Windows 10 and it protects users against all malicious software like Spyware, Adware, Virus, Worm, Trojan, Rootkit, Bootkit, Backdoor, Ransomwares and so on. Normally, Windows Defender should work without problem in background and just notify user when something is wrong or malware has been detected. However, in some cases, you might face problem with updating Windows Defender and its update failing. There are three ways to update Windows Defender:
Windows Defender Update Interface: When you open Windows Defender, you may open Update tab and then click on update and it download and install all updates.
Windows Update: Windows Update download and install updates for Windows automatically and when it downloading updates, it will download and install updates for Windows Defender too.
Manual Download from MMPC website: Users may download updates manually from Microsoft Malware Protection Center (MMPC) website.
If your PC is part of company’s network or manage by administrator, then they might configure updates through other means like local network drive or set policies to only download and install updates after approval. If you are part of company’s network, discuss issues with updates with your network administrator’s first. If you face any issue with updating Windows Defender, take a note of update error and error code and follow these steps:
Check and see whether you have any other Anti-Malware software installed or not? If you have other Anti-Malware software, it will turn off Windows Defender and disable Windows Defender update. To use Windows Defender, you will need to uninstall your current Anti-Malware software.
Check for updating in Windows Defender’s Update interface and if it failed, try Windows Update.
If it didn’t work, make sure to install all updates (if any) and restart your PC and try update again.
If problem persist, try Download and run the Windows Update Troubleshooter.
If that didn’t solved the problem, open start and search for Feedback and open Feedback Hub app and search for this issue and if it already exist, up vote it and if not, then add new Feedback. Then post your issue in Microsoft Answers forum