Both the predefined Classification security group and any custom security groups function in largely the same way, with a few important differences.
In both cases you can apply security marks to both records, folders, and categories in a Records Management site, and files and folders in a standard Alfresco site. These same marks are applied to users to set their security clearance levels.
When you classify a file or record using their Classify option, the Classify Content screen is split into two sections. The top part is for setting classification and the bottom part for applying additional security marks. You can apply both classification and additional security marks to files (or records) at the same time.
Note: Standard Alfresco permissions and Records Management permissions
continue to apply as well as any additional classifications.