Turnitin development team is familiar with many online methods posted on how to try to fool the system. This includes the "zero width space" cheat, the "white font" cheat, the "hidden characters" cheat, the "image of text" cheat, the "replacement of characters with a macro" cheat. The team is also doing regular maintenance & testing to ensure that there are no other methods that could pass round the originality report.
Turnitin strips macros from Microsoft Word Documents for Word 2003 and below. For Microsoft Word 2007, we don't accept macros-enabled (.docm) files (we do accept the standard .docx files). When we strip a macros from a Word file, whatever character the student originally had in the file will appear. For instance, one of the videos recommends starting with a "~e" and replacing it with a standard "e" using macros. When we strip the macros the "~e" will appear in the paper. This means the "~e" will appear in the Originality Report, GradeMark, and the file available for the instructor to download from the service.
Turnitin is applying thesaurus programs to switch out words for synonyms as it will search to a certain amount of difference in the source text and the match. Students can add, remove and change words and the match will still be shown.
Once the instructor looks at the Originality Report for the paper, downloads the original file & examines the content, it becomes very clear if there is something unusual with this paper or not.