Tag Archives: Windows Defender

Windows Defender not updating definitions on Windows Server 2008 and SBS2011

Windows Small Business Server 2011 Standard Edition and Windows Server 2008 R2.

Windows Updates repeatedly fails to install "Definition Update for Windows Defender".
Manually updating definitions through Windows Defender but this fails.
Running "mpcmdrun.exe -RemoveDefinitions -All" and then "mpcmdrun.exe -SignatureUpdate" but this fails with the error "ERROR: Signature Update failed with hr=8050A005".
sfc /scannow finds no errors.