A method of validating a user, includes: —storing for a user data representative of a validation code for the user including a combination of symbols from a set of symbols; presenting a displayed image including a plurality of designatable areas in which the set of symbols is distributed between said designatable areas such that each designatable area contains a plurality of the symbols; varying the image between subsequent presentations such that the distribution of symbols between the designatable areas changes between subsequent presentations, validating a user in an validation routine by detecting designation by a user of a combination of the designatable areas in a presented image, and determining whether the combination of designated designatable areas contains the combination of symbols making up the validation code for the user.