Snow Leopard Bug Deletes All Data, Apple Enters Data Loss Competition With Microsoft

The intertubes are ablaze today with reports of a serious bug in Mac OS X 10.6 Snow Leopard that, under certain conditions, can destroy all of a user’s personal data.

The problem lies with Mac OS X’s Guest Account functionality, and was first reported at the beginning of September on Apple’s Support Discussions forum. Specifically, some Mac owners have found that after using the Guest account, and later logging-in to their usual primary account, all their personal data has been wiped clean. Everything. Documents, pictures, movies, music. The whole lot.

More worryingly, some users report that they didn’t even use their Guest account first — simply booting up their Mac normally resulted in an “out of the box” experience — default wallpaper, dock configuration and, again, a loss of all personal data.

It seems just about every technology or Apple-focused website is reporting the issue this morning. At a time when Microsoft is suffering the humiliation of having permanently lost customer’s data, Apple is in similar hot water. It’s not a competition, boys!

From what the user community has managed to figure out, the bug occurs only in Mac OS 10.6 (Snow Leopard) with a Guest Account that was created in Mac OS X 10.5 (Leopard). After upgrading to Snow Leopard, the Guest Account settings retain Leopard’s older spots, to coin a phrase. And there the problem lies.

Thankfully, and in a break from its usual behavior (that is, stubborn refusal to admit anything is wrong with their products) Apple yesterday delivered a statement to CNET that reads, “We are aware of the issue which occurs only in extremely rare cases and we are working on a fix.” OK, a few plus-points for finally admitting there’s a problem. Minus a few points for it taking over a month to do so. (Seriously, do we really think it took Apple this long to reproduce the problem? No. Of course not.) And minus a few hundred more for Apple not putting that crucial statement on its own support pages, which I would modestly suggest is vastly more professional and helpful to Mac owners who aren’t CNET or tech-press readers. But oh well — at least we got something.

Thankfully there are some steps everyone can take to minimize the risks of falling foul to this hugely worrying bug.

First off, have a recent and complete Time Machine backup of your personal account and all your data (but think twice if you’re using a Time Capsule that’s a little more than 17 months old).

Next, if the Guest Account was enabled before you upgraded to Snow Leopard, pop in to your System Preferences and disable it. To do so, follow the steps below.

In System Preferences, choose Accounts

Click the padlock icon to make changes - you may be prompted for your password

The icon will now indicate you can make changes

Click on the Guest Account icon

Un-check the box labeled "Allow guests to log in to this computer"

That’s it. Close System Preferences and restart your computer. When you next log in, you can choose whether or not you want to re-enable the Guest Account. Doing so after following these steps ought to be safe, since the Guest Account will be recreated with all-new Snow Leopard settings which, it’s assumed, won’t delete all your valuable personal data. But please note carefully — this is a community-generated ‘fix’ and not officially recommended or endorsed by Apple. It might work. It might not. Your mileage, as they say, may vary.

Anecdotal Evidence Alert: I had my Guest account disabled on all my machines prior to upgrading to SL. In an heroic act of self sacrifice I’ve courageously enabled the Guest account on all of my Macs, then logged back in to my usual personal account. I haven’t lost a thing. Hardly a scientific test of the theory this problem occurs only with 10.5/Leopard flavoured Guest accounts, but encouraging, nonetheless.

Have you been hit by this bug? Can you offer a more technically sound workaround? Please share in the comments below.