I heard of a trick that a university lecturer played to test if his students were regurgitating AI stuff. The basis of the trick was beautiful in its simplicity.
When we produce a document with a word processor, we normally accept that the colour of the text will be black on a white background, as you see here. However, if the text colour is selected as white, then the text is not visible, despite the text being present on the page. There is a word within these brackets ( word ). You could see it if the font colour was not white. Wht the lecturer did was to include a word it his document bu hid it by changing the font colour. An AI helper does not take into account font colour, so the word was included in his students' responses if they simply copied and pasted what AI had produced.