How to Use SharePoint Online’s New Block Download Policy

SharePoint Block Download Policy Licensed by Syntex-SharePoint Advanced Management and Managed with PowerShell

One of the features covered by the new Syntex-SharePoint Advanced Management license blocks users from being able to download files from a SharePoint Online site or OneDrive for Business account. The idea is to protect sites that store very confidential material by forcing users to work with the files stored in the site using browsers. Users can’t even use the Office desktop apps because those apps download a temporary copy of files to work on them locally.

The block files from download feature is currently in preview. To enable a block download policy for a site, you’ll need to use the Set-SPOSite cmdlet from the latest version of the SharePoint Online management PowerShell module.

Restricting Download Access

I tested the feature by creating a new team called Project Aurora. I then configured the SharePoint Online site belonging to the team by running these commands to find all sites, select the URL for the Project Aurora site, and use it to configure a block download policy with an exclusion for site owners. In other words, site members can’t download files from its document libraries, but site owners can.

[array]$Sites = Get-SPOSite -Limit All
$Site = ($Sites | Where-Object {$_.Title -eq "Project Aurora"}) | Select-Object -ExpandProperty Url
Set-SPOSite -Identity $Site -BlockDownloadPolicy $True -ExcludeBlockDownloadPolicySiteOwners $True

The preview documentation says that site owners can grant exclusions to groups by passing the group identifiers in the ExcludedBlockDownloadGroupIds parameter. I see some issues here because Microsoft has long coached customers not to update membership of group-connected sites through SharePoint Online. In addition, adding a Microsoft 365 group to site membership creates an unsupported condition of nested Microsoft 365 groups. For now, I would avoid using group-based exclusions and concentrate solely on site owner exclusions.

After populating the default document library with some documents, I signed into the site with a member account. The site flagged the restrictions in place and removed the options to download files (Figure 1).

The Teams Files channel tab also removes the download option but doesn’t display a banner to inform the user about the restrictions. The Files channel tab does remove the option to use an Office desktop app to open a document. Before restricting downloads by policy, Microsoft recommends that you check any potential effect that the block might have on other applications, including Power Apps and Power Automate.

The file download restrictions are the same as when using a conditional access policy to limit access when users attempt to access SharePoint content from an unmanaged device. That’s the point of this feature: you don’t need to deploy conditional access policies to get equivalent protection. Although conditional access policies are a good way to control what people can do after they connect to a Microsoft 365 tenant, there’s no doubt that organizations can end up with many different policies to manage. Replacing a conditional access policy with a relatively simple download block applied at the site level might be a good thing to do, especially if you want to have finer-grained control over what sites block file downloads.

Applying the SharePoint Block Download Policy to Multiple Sites

As a practical example of how you might deploy block download policies, let’s assume that you want to stop downloads for all sites assigned the most stringent sensitivity label. In my tenant, that’s a label called “Confidential Access.” The important thing is to know the label identifier (GUID) because that’s how Microsoft 365 workloads connect to sensitivity labels. In this case, the GUID is c99e52c6-f5ff-4050-9313-ca6a3a35710f.

This script applies the SharePoint block download policy to all sites assigned the Confidential Access sensitivity label. First, we find the set of sites associated with Microsoft 365 groups. Because the Get-SPOSite cmdlet does not return all site properties when it processes multiple sites, we need to loop through the site of sites to check the sensitivity label for each site and apply the policy after detecting a matching label:

# Process sites and set the SharePoint block download policy
[array]$Sites = Get-SPOSite -Template "GROUP#0" -IncludePersonalSite:$False -Limit All
Write-Host ("Scanning {0} sites to find those with the Confidential Access label" -f $Sites.count)
[int]$i = 0
ForEach ($Site in $Sites) {
   $SiteData = Get-SPOSite -Identity $Site.Url
   If ($SiteData.SensitivityLabel -eq "c99e52c6-f5ff-4050-9313-ca6a3a35710f" -and $SiteData.BlockdownloadPolicy -eq $False ) {
      Write-Host ("Applying site download block policy to {0}" -f $SiteData.Title)
      Set-SPOSite -Identity $Site.Url -BlockDownloadPolicy $True -ExcludeBlockDownloadPolicySiteOwners $True; $i++
   }
}
Write-Host ("Finished processing. {0} sites updated with a block download policy" -f $i)

Remember Your Syntex Licenses

Remember that every member of a site that uses a block download policy to restrict downloads to site owners or groups must have a Syntex Advanced Management license. Given that you’ll probably only apply this kind of restriction to a limited number of sites, that shouldn’t be a big issue.

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