One of the most practical and efficient ways to set up a basic level of security for forms libraries and other site objects in a SharePoint site is to align your Active Directory security groups with your SharePoint permissions. Although this is not already configured out of the box in SharePoint 2010, you can achieve this by assigning Active Directory security groups to the SharePoint groups you use to grant permissions to your libraries and lists. That way, as soon as a new site user who's a member of an Active Directory security group comes online, the person is automatically granted the correct permissions to access your library documents and list items.
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