There are different ways to take over a computer. FDE protects from someone with physical access to the machine getting to the encrypted contents (ie: the entire contents of the drive, minus the bootloader in most cases) without the password. They can't crack good encryption algorithms or passwords. They could always try to steal them with physical keyloggers and such though, or they could cold boot the memory and dump the key from it if they get it while the drive is mounted. FDE also does nothing to protect from hackers. When you connect to SR you expose your system to the internet via Firefox. A vulnerability in Firefox could be exploited that will allow the attacker to take over the permissions of firefox, and probably quickly EOP to root via a desktop environment leak. Now they can remotely steal your encryption keys from memory, plus spy on everything you do and generally control your system. FDE only protects from local attackers, not remote attackers.