You may see an error message – Protection definition update failed with error code 2147023278.
It is worth noting that Windows Defender automatically and regularly updates its definition, storing the files in a dedicated folder.It would also help if you delete the contents of this folder.Please read the entire post & the comments first, create a System Restore Point before making any changes to your system & be careful about any 3rd-party offers while installing freeware.These days, more and more people are starting to consider Windows Defender as a reliable security tool.In this case, it is possible that the previous version of Windows Defender virus definition has been affected.
To get rid of this problem, it is advisable to remove all temporary files and restart the update procedure.This will switch from Microsoft Update back to using Windows Update. If it works for you fine; you can now reset the update settings to as they were earlier.7] Lastly if nothing works, there is one thing you can try: Boot into Safe Mode. Rename Software Distribution to Anand Khanse is the Admin of The Windows Club.com, a 10-year Microsoft MVP Awardee in Windows (2006-16) & a Windows Insider MVP. Are you looking for full solutions to get rid of this issue?This post will show you how to repair Windows Defender in Windows 10/8/7 so your PC can be protected from viruses.Just follow the instructions below: Those are some of the methods you can try to fix Protection Definition Update Failed error code. On the other hand, if you do not want to completely rely on Windows Defender for security, we suggest using a reliable tool like Auslogics Anti-Malware.