Configure Scheduled Scan Day

Configure Scheduled Scan Day is a Windows Group Policy setting located under Computer Configuration > Administrative Templates > Windows Components > Microsoft Defender Antivirus > Scan. It applies to the Computer Configuration branch and is classified as a Informational-level policy in the Microsoft Defender for Endpoint category.

Specifies the day for scheduled full scans (0=Sunday). Value 0 schedules scans for Sunday. MSPs should set to off-hours day.

Microsoft sets the default value to 0 while industry security baselines (CIS, NIST, DISA STIG) recommend 0.

Under the hood, this policy is enforced through the Windows registry at HKLM\Software\Policies\Microsoft\Windows Defender\Scan using the value name ScheduleDay. Modifying the value directly through regedit.exe or PowerShell produces the same effect as configuring the GPO, but going through Group Policy is preferred so that the setting is centrally managed and survives reboots, image rebuilds, and policy refresh cycles.

This is primarily an operational or user-experience setting. It does not directly raise or lower the security posture, but it standardizes behavior across the fleet, which is important for predictable support, training, and troubleshooting in an MSP-managed environment.

The policy is grouped under Microsoft Defender for Endpoint, which means it is typically applied through a domain-wide GPO linked at the OU level. In a multi-tenant MSP context, scope it through WMI filters or security group filtering rather than linking at the domain root, so that you can roll out progressively (pilot OU → wider rings → all production).

The setting takes effect after the next Group Policy refresh (gpupdate /force for immediate testing, or by default within ~90 minutes for workstations and ~5 minutes on domain controllers). For computer-side policies a reboot may be required; for user-side policies, a sign-off/sign-on cycle is enough.

1. Open Group Policy Management Console (gpmc.msc) on a domain controller or a workstation with RSAT installed.
2. Create or edit a GPO linked to the OU containing the target computer configurations. We recommend a dedicated baseline GPO (e.g. SEC – Microsoft Defender for Endpoint) instead of editing Default Domain Policy.
3. Navigate to Computer Configuration > Administrative Templates > Windows Components > Microsoft Defender Antivirus > Scan.
4. Open Configure Scheduled Scan Day and set it to 0.
5. Click OK and close the editor.
6. On the target endpoint, run gpupdate /force (or wait for the next refresh cycle), then verify with rsop.msc or gpresult /h report.html.

Direct registry path: HKLM\Software\Policies\Microsoft\Windows Defender\Scan\ScheduleDay. You can apply the same change with PowerShell:

New-Item -Path 'HKLM\Software\Policies\Microsoft\Windows Defender\Scan' -Force | Out-Null
Set-ItemProperty -Path 'HKLM\Software\Policies\Microsoft\Windows Defender\Scan' -Name 'ScheduleDay' -Value <value> -Type DWord