How secure is Time Machine backups?

March 30, 2009 10:07 AM

How secure is Time Machine backups? I'm worried about security of the data stored by Time Machine.

I'm worried about security of the data stored by Time Machine.

I have a WD My Passport external HD that I use with Time Machine for my complete backups.
But I'm worried if I lost the external HD or someone stole it.
Is the data accessible? Or it's encrypted in some way?

Is there a way to automatically encrypt it?

Because I travel a lot and I think it probably could be a big problem if it's accessible to anyone that connect it to a mac (because it's formatted to mac).

Thanks.

posted by Leech to computers & internet (17 comments total)

It's not encrypted in any way and will be accessible to anyone with a Mac. You can encrypt a Time Machine drive (Google "encrypt time machine") but it does take a bit of work to get set up properly.
posted by 6550 at 10:12 AM on March 30

There is no inherent security in your Time Machine backup. Were it to be stolen, it could be used to recover all your backed-up files. They don't necessarily need a Mac.

There are techniques to encrypt the backups, but they are not for the non-technically inclined.

If you are really worried, you might get an external hard drive with built-in encryption.
posted by procrastination at 10:14 AM on March 30

Time Machine backups are not encrypted, but you can use Apple's FileVault (built into Mac OS X) to encrypt your entire home directory. Everything in your home directory will stay encrypted in the backup. There may still be ways to get at some of the data (unencrypted caches/temp files, contents of memory, etc...), but this will certainly prevent the "random guy plugs his mac into your HD" situation and most any not involving a highly motivated attacker.

You can also create an encrypted disk image if you want to only encrypt some files instead of your whole home directory (for performance).
posted by zachlipton at 10:15 AM on March 30

To clarify, there are certain limitations when using FileVault and Time Machine together. Most significantly, it will only backup your home directory when you are logged out. Logging out will also ensure that no one with physical access to your computer can (easily) access your files.
posted by zachlipton at 10:17 AM on March 30

Time Machine backups are not encrypted, unless the files you are backing up are themselves encrypted. You can combine Time Machine and FileVault in a limited way. The two main drawbacks are that (1) the encrypted home folder will only be backed up after you log out and (2) you can only restore the entire home folder, not individual files or subfolders.

Technically there is a way around (2), but it's fairly technical. It is possible, though, that Apple will enable individual file and folder restore of FileVault protected data in 10.6 ("Snow Leopard").

If you only have a few particular files that you need to keep encrypted, then I would recommend a file-oriented encryption program like MacGPG2.
posted by jedicus at 10:21 AM on March 30

Here is a better link to encrypted external drives.
posted by procrastination at 10:21 AM on March 30

Thanks guys.

Yes, definitely FileVault is not the best choice, because I need to access to backed up files. So it will be useless if I need to restore all my home folder when I need something.

I'm looking at the links you guys posted and seems like there's no solution other than encrypt files previously.

What about TrueCrypt? I've heard that Time Machine doesn't recognizes TC drives, any luck?
posted by Leech at 10:37 AM on March 30

I don't trust FileVault. I use the disk image model zach mentions, with a few encrypted disk images (4-8Gb) for "Home" and "Work" and "R-Rated Pics" and so on. They're very secure, but they'll be slow performance hogs with Time Machine, since their entire "file" will be backed up each time.
posted by rokusan at 10:38 AM on March 30

I don't trust FileVault. I use the disk image model zach mentions, with a few encrypted disk images (4-8Gb) for "Home" and "Work" and "R-Rated Pics" and so on. They're very secure, but they'll be slow performance hogs with Time Machine, since their entire "file" will be backed up each time.

A couple of misconceptions here that may be unintentional:

Filevault protected home folders are disk images, under Leopard they are sparse-bundles, in Tiger they were sparse-disk.

In sparse-bundles only the changes to parts of the bundle that hold the impacted data are updated when changes are made to the unencrypted bundle image. Time Machine and other backups (SuperDuper!/etc) will only update the delta in the data, making your actual backup times smaller as the entire image is not changes as it was under Tiger. Yes you still need to be logged out of the filevault account for Time Machine to conduct backups. As mentioned above there is hope that 10.6 will contain tighter Filevault and time Machine integration.
posted by iamabot at 10:54 AM on March 30

If you use sparsebundles for your disk images, then only the 8MB bands that have changed need to be backed up. They work much better with Time Machine.
posted by kindall at 10:56 AM on March 30

I hope for that FileVault and Time Machine integration.

I'm going to try true crypting the external HD, let's see if Time Machine recognizes it.
I'll tell you the results.
posted by Leech at 10:59 AM on March 30

I didn't realize sparseimages would be backed up incrementally. I'm not even sure how that's possible with encrypted images, since the bits could be scattered (?), but I'll take y'all's word for it!

So that means encrypted disk images is definitely the way to go. The "one big file to sync" was the only downside to me.
posted by rokusan at 12:17 PM on March 30

Well, no. Truecrypt solution didn't worked. Time Machine doesn't recognizes my TC hd. :(
posted by Leech at 2:21 PM on March 30

You could try using Carbon Copy Cloner and ditching TM. It looks like CCC will create an encrypted back up image of a disk, and there appear to be settings for full and incremental backups. I'm not quite sure how you'd go about doing that (I've only used it to clone a HD) but it's worth trying.
posted by 6550 at 2:35 PM on March 30

I don't really understand your reason for rejecting FileVault:

Yes, definitely FileVault is not the best choice, because I need to access to backed up files. So it will be useless if I need to restore all my home folder when I need something.

Or at least, the reason I think you're stating is not correct.

If you encrypt with FileVault and then backup with Time Machine, at least to the best of my knowledge, you can still access individual files from the backup volume. It just involves an extra step, versus recovering from an unencrypted volume: you need to mount the "disk image" that contains the encrypted copy of your home folder.

See this hint; relevant portion reprinted below:

If you need to restore files in your encrypted home directory, the Apple warning is correct in that you can't use the Time Machine application's 'galaxy' interface to do so. However, you can restore them using the Finder.

Double-click on your backup drive, and you'll see a folder called Backups.backupdb. Double-click it and you'll see a folder with the name of your machine. Double-click that, and you'll see a bunch of folders named with dates and times. Double-click the one from which you want to restore the file(s), and double-click your way down through your startup disk name, then Users, then your username.

You'll then see a package called username.sparsebundle. Double-click it, enter your login password, and a copy of your home directory will mount. You can drag files off of this copy -- just don't drag any files onto it or delete any files! After you are done, eject the mounted home directory to avoid confusion. There isn't any reason that Apple couldn't automate the restore process; apparently they ran out of time when releasing version 10.5.

posted by Kadin2048 at 2:44 PM on March 30

@Kadin2048
So everything backed up in Time Machine if I'm using FileVault is stored as simple files, but encrypted?

I still don't like the idea that FileVault only works while I'm logged out. In a macbook I rarely have it on but logged out.
posted by Leech at 3:24 PM on March 30

I didn't realize sparseimages would be backed up incrementally. I'm not even sure how that's possible with encrypted images, since the bits could be scattered (?), but I'll take y'all's word for it!

No need to take anyone's word; the way it works is easily explained. With a sparsebundle disk image, the disk image is stored not as a single file but as a folder containing as many 8 MB files as are needed to hold the contents of the volume. The computer then reads from or writes to the appropriate file in that folder when a particular block is requested. The great thing is, it only creates files when necessary. I created a 200 GB encrypted disk image and it took only 150 MB on disk. As I add new files to the disk image, that will grow, of course.

Time Machine can't back it up at the granularity of an actual file, but any change you make will likely be limited to one or a few 8MB chunks of the disk image, and so Time Machine can back up some smaller fraction of the file than the whole thing.
posted by kindall at 3:36 PM on March 30