Patent ID: 8646078

Claim:
One or more computer-readable storage media devices storing instructions, that when executed by a computing system, cause the computing system to perform operations comprising: reconciling a reported multipurpose internet mail exchange (MIME) type, included with a file that is downloaded, with a sniffed MIME type determined by the computing system, the reported MIME type having an associated cache file extension; replacing the associated cache file extension of the reported MIME type with an updated cache file extension responsive to ascertaining that the sniffed MIME type does not match the reported MIME type, the updated cache file extension being referenced by a class identifier (ID) associated with the sniffed MIME type; reporting a reconciled MIME type to a class ID sniffer, the class ID sniffer configured to determine the class ID based on content of the file, the updated cache file extension, and the reconciled MIME type; and executing the file in an executable shell determined from a security matrix that includes the class ID and the updated cache file extension, the security matrix including a set of user interface definitions mapped to a security level assessment based on the class ID, the updated cache file extension, and one or more associated registered types.