A method, system and product including: obtaining a graphical user interface (GUI) element of a GUI of the end device, wherein the GUI element is associated with a text string that is included in the GUI; transforming at least a portion of the text string according to a transformation function, thereby obtaining a fully or semi-transformed text string, wherein the semi-transformed text string comprises a transformed portion and a plaintext portion; providing to a server the fully or semi-transformed text string, whereby the server is enabled to perform string-based analysis without being exposed to a content of the text string.