Abstract: An apparatus and method of preventing unauthorized access to computer data. The apparatus is installed in a computer system between the main board and an associated data storage device, for example a hard drive. Read/write commands from the motherboard to the hard drive are intercepted and scrutinized by a filter means of the apparatus. If the pre-determined level of data access of the user issuing the command is insufficient to permit the type of access that is being sought (eg: write access is sought, but the user only has permission for read access on that particular hard drive partition), then the command is blocked. An identity means, for example an RFID, may also be included that identifies an authorized user and corresponding level of data access. The apparatus and method may be employed as a stand-alone solution or as part of a computer network.