Just giving a warning for anyone who uses this tool:
Nintendo has started giving out MAC bans to people who get banned on Miiverse too much. No amount of SecureInfo_A editing can fix it, and you're also restricted from online services, so you can't do online multiplayer after it.
@ariankordi and
@consumeroffood have gotten them, as well as me, so keep in mind that you're risking loss of features if you do that.
Note that this only applies to those of you who do it quite a lot, as it took over 100 accounts made by me for this to happen. Also, as MAC addresses are console-specific, users with more than one 3DS can switch to another if that's an option. I wanted to inform you all on this, to make sure all warning are in place.
Thank you for your consideration.