1. A method of securing data stored on a computer system, the method comprising: generating a password comprising a plurality of values; securing data stored on the system using said password; implementing a two level authorisation procedure to enable user access to said secured data, a first authorisation level requiring user input into the system of only a subset of values selected from said plurality of values and a second level requiring user input of the entire password; and wherein if a mistaken entry is made in the first level authorisation, a second level authorisation is implemented, and wherein each time said first level authorisation is implemented, the input of a subset of values reselected from said plurality of values that differs from that subset selected for the preceding implementation is required.