How can I speed up Windows Defender full scan? It works but is very slow. Thanks. Pete.
Full scans can take a long time just because they have a lot of ground to cover (a large number of files to scan); so uninstalling unused programs, removing unneeded files and System Restore points, and frequent use of the Disk Cleanup tool can all
help a little. Full Scans also tend to take a long time because they take extra time to unpack and scan the contents of archive files when they run with the default setting for the
-DisableArchiveScanning parameter. So you might want to disable archive scanning and see if that significantly reduces the scan time – but this is something that I wouldn’t generally recommend:
Indicates whether to scan archive files, such as .zip and .cab files, for malicious and unwanted software. If you specify a value of $True or do not specify a value, Windows Defender scans archive files.
The documentation for the -DisableArchiveScanning parameter is wrong. This parameter is actually set to False (Disabled False) by default, which means that archive scanning is enabled. You can confirm this by running the
Get-MpPreference command in PowerShell. So in order to disable archive scanning you would run this command at the elevated PowerShell prompt:
Set-MpPreference -DisableArchiveScanning $True
Also note that the initial Windows Defender Full Scan will always take extra time because Defender will be preoccupied with checking the “reputation” of files as it builds up a cache of trusted files that don’t need to be scanned. And of course there
are also some error states that will result in excessively long scan times; most notably, the presence of a real-time third-party AV app, or remnants thereof.
Users should also be aware that Defender’s scheduled scans still run with their CPU utilization capped at 50%, even though the Automatic Maintenance scan now runs strictly in idle time – where it has no impact at all on system responsiveness. So in
order to get the Automatic Maintenance scan (or any independently scheduled scan) up to full speed, you will need to run this command at the elevated PowerShell prompt: