If I pair my Android phone and my laptop, I can share files over Bluetooth from the phone to the laptop. I’ve started finding this a really convenient method for me to send files to a Linux laptop without needing to install a separate app on either the phone or my laptop. Especially when I’m away from my home network (I use SFTP at home).
How secure is this? Is there encryption by default and could someone else nearby with a receiver potentially decode the file you’re sending?
The firmware on the devices likely isn’t updated much by the manufacturers.
So “it really depends”
Unfortunately unlike WiFi, the encryption is built into the firmware in ways that don’t update much because they make everything backwards compatible so you don’t notice.