How do you know firmware doesn't contain malware?

[Pulseczar1]

I'm trying to use a phone that will not boot up. I think that there's a good chance that reinstalling all of the original software on the phone will bring it back to operational. I could quickly jump in and follow some directions on the dozens or hundreds of sites out there providing instructions to do this, but I want some sort of guarantee that the software is legit and does not contain malware. Is there any assurance out there, or does everyone just cross their fingers and trust random strangers on the internet? Does Motorola provide any checksum hashes for their firmware, so that one can use them to verify the authenticity of so-called 'stock' software? Or is there a way to download the firmware directly from Motorola?

 

[sd_shadow]

I'm trying to use a phone that will not boot up. I think that there's a good chance that reinstalling all of the original software on the phone will bring it back to operational. I could quickly jump in and follow some directions on the dozens or hundreds of sites out there providing instructions to do this, but I want some sort of guarantee that the software is legit and does not contain malware. Is there any assurance out there, or does everyone just cross their fingers and trust random strangers on the internet?

If the bootloader is locked (see AP fastboot mode), only official firmware can be flashed in AP Fastboot mode.

Does Motorola provide any checksum hashes for their firmware, so that one can use them to verify the authenticity of so-called 'stock' software?

no.

Or is there a way to download the firmware directly from Motorola?

For most devices No, Most Motorola Firmware is pulled from Official Motorola servers, using special methods. There are only few Non-Motorola employees, that know how to do that, and don't share their methods, so Motorola does not close the door.