I'm thinking about using an AirPort Time Capsule for my Time Machine backup. I would certainly use encryption, but I'm still concerned about sensitive backup data sitting on a networked routing device that could get compromised.
The Apple website has this to say on backup security:
Don’t back up sensitive data to a network disk if you don’t trust the network administrators who control the disk. Instead, select a backup disk that’s under your own control, such as an external disk connected to your Mac.
This is a bit vague and it might simply refer to Time Capsules with multiple user accounts, so I'd like to know specifically: If there's some vulnerability in the AirPort Time Capsule and an attacker manages to compromise it and take over the Time Capsule by running arbitrary code on it, are my encryption key and the backup contents safe from them? I think this question breaks down into 2 parts:
- Does OS X encrypt everything locally and only send encrypted data to the Time Capsule?
- If an an attacker controlling my Time Capsule tries to trick OS X into doing an unencrypted backup, will OS X warn me first?