“instead, they would install an app that would train itself on your voice over time... improving its voice to text conversion.”
And to take that one step further, they could fix the app so that it would erase itself if you started searching apps on your phone. Then, it would automatically upload after you stopped searching. You would never know if they listened to you illegally.
it wouldn’t bother removing itself. it would just modify the search software to insure it was never seen or reported (if those modifications aren’t already built in)
btw, they can do something similar to desktops.
nic cards have a nifty ability to allow a remote hacker to upload boot code then boot the box. done right, the uploaded code would dnload and install the necessary agent and log out, resetting the boot record (covering its tracks). the agent would then work with the existing system (previously compromised for the govt by microsoft and apple) and start recording / translating / uploading.