[peterwwillis]

Some hardware comes with firmware that can't be overwritten unless it's properly signed by the manufacturer to prevent an attacker from being able to get low-level control of devices that couldn't otherwise be detected. Example: https://www.cisco.com/c/en/us/products/collateral/security/c...

It is, of course, possible to replace an entire physical device with your own hacked one, and have nobody be the wiser. But the theory goes, that would be a lot harder than just copying rooted firmware into a device remotely. (The above system was hacked this year, though)