Well, at the moment, my copy of the Nintendo Network ID applet is broken, and I'm trying to fix it so I can use the NNID Settings app properly. It gives me an error telling me "you must connect to the internet to use this app" when I do anything in it, despite the fact that my internet is clearly working and everything else on my 3DS that I haven't modified works just fine. Once I fix that, I plan to run some testing, and then get in contact with a more experienced developer like @Nanquitas to see if a CFW or NTR plugin can be created to replace the DeviceCert in RAM with the files from another unbanned 3DS. Maybe then we'll have a fix to the issue. I probably won't respond to PMs asking for my old proxy applet that I've mentioned previously, as the proxy has proven to be really unstable and I still haven't tried to decrypt the New 3DS version of the applet. If I can't fix my 3DS's NNID applet soon enough, I'll instead release a bunch of information I have on account.nintendo.net with PC-compatible examples so you can all do your own research. I can't give an exact answer, but the BOSS applet sends certain information to Nintendo's servers whenever you do certain things like running an app (for the Friend List, for example), and everything else you do involving their servers. As one of the biggest companies out there, they take a LOT of analytics from everything they can take them from. Nintendo Network ID stuff for example is known to be heavily tracked by them, I've found secret things on their server that were quickly patched and my account banned solely because they knew where to look for me and I used their functions once. I was also able to see some of my dev NNID usage on the Account Developer Portal, and they have way more information internally than their public dev tools show. They've been collecting information on this stuff for a while, and only now are they starting to use it. Nintendo knows all.