Its currently unknown exactly how Nintendo is detecting end users of these flashcarts, but some people are suspecting its only affecting people who are choosing to use Public Headers (which act almost like a CD-Key on a PC game) which are supposed to be unique to each individual copy of a game and that Nintendo is banning people who are caught using the same “key” or header at the same time. Or perhaps that they’re using one that Nintendo is aware is out there for anyone to grab.
Of course this method of detection is solely based on speculation so take it with a grain of salt, until someone well known in the 3DS scene has a chance to fully analyze what’s going on here. My advice to users of these and any other flashcarts for the 3DS, don’t play any backups online. Use your flashcart for offline gaming only and it might be a good idea to turn off wifi capabilities on your 3DS when doing so if you’re super paranoid :P).