A computer system includes hardware for selectively disabling alteration of data residing on a mass storage device which is subject to remote access. In one embodiment, a hard disk drive is operated in a conventional manner including both read and write modes when the system is being operated in a non-secure mode of operation, such as when remote access is not allowed. In a secure mode of operation, a locally operated switch is used to disable writing to the hard disk drive to maintain data integrity on the drive. The system may also include first and second electrically isolated buses and corresponding processors. In this configuration, the hard disk drive may be selectively connected to the first bus and processor for the storage of data, or to the second bus and processor when in a secure mode to provide for read-only remote access to the information stored on the hard drive. A write-only hard drive may also be included for storage of confidential information provided by remote users so that other remote users cannot access that information. In a master/slave processor configuration, all system programming is resident in an isolated portion of the system inaccessible to remote users. The slave processor receives instructions only from the master processor so that the operation of the slave processor cannot be compromised by viruses uploaded by remote users.