How to change your Facebook privacy settings

With the appearance this week on a torrent site of a list containing the user names and profile addresses of more than 100 million Facebook users, attention has returned to the thorny business of keeping your private details private on the social networking site. Here's how.

For a moment, we'll ignore the intricacies of the privacy settings controlling who can see which bits of information within Facebook itself. The thing that got 100 million users into Ron Bowes' Big Black Book was the fact that they hadn't prevented their Facebook profile form being catalogued by Google and other search engines.

Opting out of search
To do this, you'll need to log into your Facebook account, click on the drop-down Account menu, and select Privacy settings.

At the bottom of the page, you'll see a section marked Applications and websites. Click the 'Edit your settings' link.

Find the Public search section, and click the button marked 'Edit your settings'.

Here, you'll be able to view a preview of what details from your profile anyone can see - including non-Facebook users, and anyone who has simply found your page using Google or other search engines. If you haven't already done so, to prevent your profile from appearing in search engine listings, uncheck the tickbox marked 'Enable public search', and click Confirm.

One thing to note: if you're already one of those users contained in Ron Bowes' torrent, there's little you can do to prevent your account from being 'found' using the list - concentrate on protecting what info is publicly available, or - if you haven't already done so - change the user account name, so that an attempt to follow the URL in the file will result in a 'page not found' error.

With that done, your profile will only be accessible by searching within the Facebook site itself. Exactly what information you want to make public to these people is a matter for you.

Sharing with friends
Even using Facebook's recently simplified privacy settings, achieving a decent level of security is a painstaking business.

You'll find options to control how easily you can be found on the site under the 'Basic directory information'.

The Sharing section allows you to define the specifics of who can see your pictures, wall comments and other profile elements - we'd recommend setting them all to 'Friends only'. And while joining a network may seem like a good idea, remember that it makes your details accessible to everyone in that network.

Applications and games
Other settings that affect your privacy include those that enable applications or other websites from accessing your data. You'll find these under 'Applications, games and websites'.

One major way in which your personal info can leak is through Facebook's platform applications, which will effectively hand your public details to a third-party developer or site owner. Here, again, it's your call: if you really, really can't do without games like Farmville or apps like 'How well do you know your friends?', then you'll have to take the consequent loss of privacy.

We'd personally take the route of turning off all platform apps - but if you want to pick and choose, one setting we would tweak is to turn off 'Instant personalisation'. This is the cornerstone of Facebook's much-trumpeted 'open graph', and enables partner web sites to take a look at your likes and dislikes in order to tailor their content - and, ultimately, flog you stuff. Remember that every person you allow to share your data is a potential weak point. So if in doubt, deny them the opportunity.

It's also worth making sure third parties can't get at your information via your friends - you'll find this setting on the same page.

The nuclear option
If all that sounds like a lot of hassle, there's always the one-stop solution. Do you really need to be on Facebook? If not, then consider deleting your account.

Previously, deleting your account has proved a near-impossible task.

In your privacy settings, you'll find an option to deactivate your account. This simply puts your data on hold, and will not delete it from Facebook's servers.

If you really want to go the whole hog, log in and follow this link.

Click Confirm, and - here's the crucial bit - make sure you don't attempt to log into your account 'just to check' if you've been deleted for at least 14 days. Any attempt to access the account, and the deletion process is reversed.

Facebook is reportedly testing a new, immediate deletion tool on selected user accounts, but this is not yet publicly available.

One last thing to note: comments and other content you've put into the public domain, or other people's walls or within group discussions, will not be deleted. They will remain on the site, attributed to an anonymous Facebook user.