Is it possible to completely disable the WiFi on the Raspberry Pi 3? Meaning no wireless connection at all for eternity?
I think the best way is just to physically cut off the antenna from the board itself, but will it damage the Raspberry?
In raspbian do:
aptitude purge firmware-brcm80211
This way the wireless firmware wont be loaded at boot time. In addition, it will save RAM too.
No transmitter will "like" an antenna being just cut off - it will fry for sure. Disable the built-in WiFi hardware in your OS, or - if it's a privacy concern - in your OS image disable the specific device support by VendorID/DeviceID pair, so there will be no way to detect it. If you need even more security+privacy - play with dtb-lists to prevent even an externally-built module to detect the WiFi chip and use a kernel modules signature check. But don't cut off the antenna - it's not the way it's done properly
Have a look at the
rfkill program to disable wlan and bluetooth on the software level. I think some chips will turn off completely, others just stop transmitting anything.
I think that any kind of software has a backdoor, e.g. a creator of a software knows how to bypass it, or professional hackers learn how to attack "disabled" WiFi and Bluetooth computers
Therefore there's no way of 100% protect the Raspberry Pi 3, and I don't think there will be any future Raspberry Pi without wireless connectivity