Get-SmbShareAccess -name $ShareName | Foreach {Revoke-SmbShareAccess -name $ShareName -AccountName $_.AccountName -Force}
Gets all the permissions for the share, then revokes them.
PS C:\> $ShareName='ScriptFiles
>> Get-SmbShareAccess -name $ShareName | Foreach {Revoke-SmbShareAccess -name $ShareName -AccountName $_.AccountName -Force}
Name ScopeName AccountName AccessControlType AccessRight
---- --------- ----------- ----------------- -----------
ScriptFiles$ * NT AUTHORITY\SYSTEM Allow Full
ScriptFiles$ * *S-1-5-5-0-158796760 Allow Read
ScriptFiles$ * *S-1-5-5-0-158796760 Allow Read
ScriptFiles$ * Everyone Deny Full