Facebook has rolled out its facial recognition technology to countries outside of the US, but has switched the feature on by default without telling its users first.

UK-based security expert Graham Cluely noted earlier today that Facebook had slotted the tech into the social network.

The tech works by scanning newly uploaded pics and then identifies faces from previously tagged photos already stored in Zuckerberg's internet silo.

When the software was introduced in the US late last year, Facebook pointed out that users could disable the function.

"If for any reason you don't want your name to be suggested, you will be able to disable suggested tags in your Privacy Settings," the company wrote on its blog post last December.

But now that the tech has reached other shores, Facebook clearly didn't feel the need to alert its international stalkerbase that its facial recognition software had been switched on by default within the social network.

The "Suggest photos of me to friends" feature in question is located in the company's privacy settings. Facebookers need to click on "customise settings" before being able to access the function and disable it, if they so wish.

"Unfortunately, once again, Facebook seems to be sharing personal information by default. Many people feel distinctly uncomfortable about a site like Facebook learning what they look like, and using that information without their permission," said Cluley.

"Most Facebook users still don't know how to set their privacy options safely, finding the whole system confusing. It's even harder though to keep control when Facebook changes the settings without your knowledge."

He said Facebook shouldn't require its users to constantly check their privacy settings to see what the company has changed since their last visit to the site.

"The onus should not be on Facebook users having to 'opt-out' of the facial recognition feature, but instead on users having to 'opt-in'," he said.

"Yet again, it feels like Facebook is eroding the online privacy of its users by stealth."