Lately, I have been somewhat preoccupied with the security of my computer. Not that I had actually anything to hide, but I just do not want anyone pilfering my data.

So, I set up FileVault in OSX, which effectively encrypts all my data with minimal fuss. The password is set to something long that only I know and the system password is something equally strong and secure. The system password is resettable using the install disk though, so it is essentially rather useless to obsess about it too much. Do you know if resetting the system password gives access to the FileVault password? This would basically render FileVault useless.

Additionally, I need a backup solution, so I set up both Time Machine and Dropbox. Now my question is: The password to the Dropbox account is saved in the Browser of my Windows 7-machine and the Dropbox-App on my iPhone. While both are password-protected and do not have actual copies of my files, I figure that these are the weakest links in my data security.

Do you think there is a simple way to improve on this set up? Or do you think I this is rather obsessive already?

  • 1
    As a side note: Time Machine won't backup your FileVault folder unless you log off. support.apple.com/kb/HT3446 -- You can turn on FileVault to encrypt data stored in your home directory. This data will also be encrypted in the backup. [..] When using FileVault, you cannot restore individual files in your home directory via the Time Machine browser. However, you can restore all files and folders by using the Restore System from Backup feature of the Mac OS X Installer. Important: Time Machine will perform backups only when you are logged out of your FileVault-protected account.
    – Arjan
    Oct 4, 2009 at 13:30

5 Answers 5


I'm not sure what you mean by "system password". If you're talking about the password to an admin account, or even root, then it's not an issue; FileVault security is completely independent of overall OS security (well, with one exception: if someone subverts the box, installs something like a keylogger, then hands it back to you and captures your FV password as you log in...).

OTOH, if the "system password" you're talking about is what the Security prefs calls the "Master password", then anyone who guesses it has an easy backdoor into your FV. But it's not resettable with the install disc, or any other method that doesn't involve knowing it to begin with. So that's not really a worry.

Now, on to backup security: Time Machine's not a problem (with the caveat Arjan mentioned, that it can't back up your account while you're logged in) because it backs up the encrypted data, so it has essentially the same security that FV itself has. You do have some minor annoyance when restoring, because TM's slick restore interface can't see into the backed-up FV, so you have to manually mount the backed-up image and then root through it by hand. (Ok, one more minor qualification: since Time Machine will store multiple versions of the encrypted data, it may be possible to tell something about what's going on inside of FV by looking at how the encrypted version changes; I haven't seen anyone analyze FV for its resistance to this type of attack.)

TFM's basically right about backups you don't have control over, if you're backing up the unencrypted version of your files. If you're backing up the FV encrypted version, then you're back in the same situation as with TM: it's (mostly) automatically secure, but you've got the annoyance of only being able to back up while logged out, and restoring anything'll mean downloading an entire snapshot of the FV image, manually mounting, etc.

I'd recommend looking a program designed for encrypted online backup; done right, this encrypts everything before it leaves your machine (so you aren't dependent on the security of the repository) and is still easy to restore from. Unfortunately, I haven't done the necessary research to be able to recommend a specific solution that "does it right" (and I'm sure there are lots that do it wrong).

  • Dropbox sais: * All transmission of file data and metadata occurs over an encrypted channel (SSL). * All files stored on Dropbox servers are encrypted (AES-256) and are inaccessible without your account password * Dropbox employees are never permitted to access user files, and when troubleshooting an account they only have access to file metadata (filenames, file sizes, etc., not the file contents) This sounds reasonable. The question probably is, if it is my PC that does the encryption or if this is done online.
    – bastibe
    Oct 5, 2009 at 8:06
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    Any way of verifying Dropbox's comment?
    – TFM
    Nov 4, 2009 at 19:32
  • Better still, any way of verifying that your data would be safe from government inspection?
    – Everett
    Nov 22, 2010 at 10:02
  • @Everett given the existence of National Security Letters, i'm pretty sure the answer to that is "no". And other countries (than the US) are sometimes even worse... Even though I don't personally expect to be the target of a national security or even criminal investigation, the idea of someone else holding encryption keys for my data just plain makes me nervous. Nov 22, 2010 at 18:54

A third party solution like Dropbox should always be considered insecure, as you leave your data in the hands of a company you cannot "see or touch". Such companies might operate under the laws of another country which permits/forbids differently than the country you live in, and therefore making any legal actions nearly impossible in case of abuse.

Furthermore, companies get sold and bought. A reputable provider offering an online solution can be bought, and the data can fall into hands of people whose main purpose with this trade is exploiting this opportunity.

I'm not trying to say that you should be paranoid, but use your common sense when choosing an online backup/file storage provider. Google the company name, read reviews about the service, etc.

  • This comment is really ill-informed. DropBox uses encryption and Amazon S3 so you can still get access to your files. Also, see Paperflyer's comment above. Nov 4, 2009 at 13:21
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    Well, so says DropBox. As long as I have no way of verifying any encryption on the server, I consider all online backups as "insecure".
    – TFM
    Nov 4, 2009 at 19:31

I know a little bit about DropBox's security. The data is encrypted on S3, but DropBox holds the encryption keys, not you. (so they could snoop if so inclined). If you want to hold the keys, you need JungleDisk or similar. Of course there is a downside to having the keys on your side... if you lose them you're screwed.


I would suggest if you want to use DropBox for cloud storage of any sensitive information that you create a TrueCrypt volume/folder in your DropBox. There are instructions on DropBox on how to do this. In fact, security issues are plaguing DropBox right now in the online media and there are many blogs/articles about using TrueCrypt with DropBox that should rank highly on Google if you search. (Lifehacker recently blogged about it.)


The only service, since 2007, that I know of where you can rest assured a data-breach would not reveal any of your data is spideroak.com Review at http://freelanceswitch.com/general/backup-your-computer-spideroak-review/ explains:

"Sure every backup service provides encrypted backup, but SpiderOak takes things one step further with their zero-knowledge privacy policy. That means that your files are even encrypted from staff at SpiderOak." And from everyone else in the world except you using the decrpytion key you generate.

The source-code for spideroak software is available so it should be possibly to verify with mathematical certainty strength of encrpytion, and that a key known only to you is required to decrypt: https://spideroak.com/code Just don't loose that key as no one can help you get the data back. In general, you run into a trust issue at some point with any non-open-source propietary solution. Which is a very strong point with open-source solutions. I would not trust any sensitive data (tax returns, medical records) to any system for which source code was not available.

You could of course use encryped files or file-containers like TrueCrypt with Dropbox, google and the others. But that is clutzy extra step compared to the spideroak methodology namely encrpytion on the fly on your own hardware. And would be tricky if not impossible to do on iPhone (where there is a spideroak app!).

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