Is there a feasible way to safely use a pre-owned smartphone? For a PC/Laptop I would simply shred the contents of the hard disk drive before creating new partitions. If feeling paranoid, I might even flash the BIOS (see also this question). I'm considering to buy a used smartphone (for environmental purposes), but how would I make sure it is free from any irregular spyware (apart from the standard Google stuff)? Can I take the same approach as for a PC and still use it as a regular smartphone after? Rooting would give me "similar access to administrative (superuser) permissions as on Linux", although in reality I don't need root to shred a PC as long as I have physical access, although it may be harder to exploit physical access to a smartphone than for a PC. Naively, I would expect:
- Shred the contents of any read/write-storage on the smartphone, either by mounting it on Linux (assuming I get access to all storage media that way), or by booting it into the right mode (assuming I can get into the bootloader — perhaps I can boot into a custom OS from an SD-card?);
- Repartition the disk (remark above applies);
- Install a version of Android on the disk, presumably with something equivalent to a distribution so I have a kernel and a minimum of software for it to function;
- Reboot and use it as if it was new.
Are such or equivalent steps feasible for an ordinary user with moderate technical know-how? Or am I totally on the wrong track as far as making a pre-owned smartphone safe to use is concerned?
For the purposes of this question, assume a smartphone designed to run Android and released in 2015 or later.