Security systems frequently rely on warning messages to convey important information, especially when a machine is not able to assess a situation automatically. There is a significant body of work studying the effects of warning message design on users with numerous suggestions on how to optimise their effectiveness. Design guidelines and best practises help the developer to display urgent information. In this paper, we present the first empirical analysis on the extent of the influence of linguistic properties on the perceived difficulty of the descriptive text in warning messages. We evaluate warning messages extracted from current browsers and present linguistic properties that can improve a warning message text’s perceived difficulty. Our results confirm that, while effects of attention, attitude and beliefs are at least as important as the linguistic complexity of the text, several steps can be taken to improve the text’s difficulty perceived by the user.