Hello @Andy Panyanouvath ,
You could try the following cmdlets to disable Everyone group:
if(!(Get-PSSnapin Microsoft.SharePoint.PowerShell -ErrorAction:SilentlyContinue))
{
Add-PSSnapin Microsoft.SharePoint.PowerShell
}
$claimMgr = Get-SPClaimProviderManager
$allUser = get-spclaimprovider –identity "AllUsers"
$allUser.IsEnabled = $false
$claimMgr.Update()
Here is a similar case for you reference:
https://social.technet.microsoft.com/Forums/sharepoint/en-US/ad63bd73-5070-493c-a358-30d4ab07cdcb/how-disable-everyone-group?forum=SP2016
Thanks,
Echo Du
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