Abstract: A method of, and system for, generating an image for use in monitoring interaction between a user and a computer is provided. The method includes generating random reference data wherein the reference data comprises a plurality of characters and randomly selecting a font from one of a plurality of fonts. Each font may comprise a plurality of font images and a font image may be retrieved for each character of the reference data. Thereafter the retrieved font images may be combined. In one embodiment, each font image includes a font background and a user identifiable character defined by removal of the font background so as to define the user identifiable character. In addition or instead, each font image may include a font background including a plurality of font patterns, and a user identifiable character defined by a concentration of the patterns so as to define the user identifiable character.