When Transmission had an infected release a couple of months ago, I remember reading that the malware had in-progress features to encrypt Time Machine drives. It gets installed, waits a couple of days, locks up your hard drive and any backup drives that you connect, and there's nothing to do about it.
That's enough to hose 99% of users, even the ones following traditionally sufficient practices. You're only safe if you have offsite backups with drives that didn't mount to your computer recently.
That's enough to hose 99% of users, even the ones following traditionally sufficient practices. You're only safe if you have offsite backups with drives that didn't mount to your computer recently.