You know those really unflattering photos on Facebook that you untagged at lightning speed? Now might be a good time to delete them ... or at least check up on one new privacy setting.

Yesterday, security firm Sophos issued a warning saying that Facebook rolled out a feature that recognizes your face in photos, prompting your friends to tag you.

Some Facebook users in the United States have had this feature since it was first announced in December. The difference: During the beta, there was no setting to opt-out of appearing in tag suggestions. As of yesterday's rollout, however, you must now adjust a setting in order to opt-out.

According to Facebook, this facial recognition feature uses a comparison of photos you're tagged in to suggest that friends tag you in new photos. The site says that this feature is intended to save you time: Instead of tagging the same friends in 25 photos you just uploaded, you can now apply one label to multiple photos in one step.

Facebook reiterates that only friends can tag you in photos, you'll be notified when someone has tagged you, you can remove a tag whenever you want and that tag suggestions are based only on photos you've allowed yourself to be tagged in.

Here's how you can opt out of this feature.

Facebook Facial Recognition: How to Opt Out

Facebook has automatically opted you in to this new facial recognition feature, which means your friends will see suggestions of photos in which to tag you, unless you change the setting.

To turn off this feature, go to "Account ," then "Privacy Settings" and select "Customize settings." In the second section, "Things others share," click "Edit Settings" next to "Suggest photos of me to friends."

<[Want more tips, tricks and details on Facebook privacy? Check out CIO.com's Facebook Bible.]

Then, change the setting from Enabled to Disabled. Do note that friends can still manually tag you in photos.

How to Remove Your Summary Information from Facebook

Facebook requires two types of information in order to automatically suggest that a newly uploaded photo looks like someone who's been tagged on Facebook before.

The first is information about photos you're tagged in. For example, when you're tagged in a photo, Facebook associates the tags with your account, compares what these tagged photos have in common and stores a summary of this comparison.

The second type of information compares your new photos to stored information about photos you're tagged in. So, when you or your friends upload photos, they may be compared automatically to the summary information Facebook stores about what your tagged photos have in common. The result of this comparison may also be used to group photos or suggest that photos look like you.

To remove the summary information stored about you for tag suggestions, you must contact the Facebook Photos Team. To do this, visit the Facebook Help Center here, scroll to and expand the very last question on the page, and click the "contact us" link.

A pop-up box will appear to send an automated request to the Facebook Photo Team. Click "Okay" to submit your request.