[Term] user search security filter [Definition] 
The user search security filter that specifies group and user permissions for a specific FAST Search user. FAST Search Authorization (FSA) filters out inappropriate search results by intersecting the user’s query with the user's search security filter, and checking each document’s access control list to determine if the user has permission to view that document. The user search security filter is FSA's primary means of enforcing document-level security ("security trimming"), which helps to ensure that search results display only documents that the user has permissions to read.