Social media giant Facebook is planning to secretly watch and record users through their webcams and smartphone cameras.

"According to a newly discovered patent, the company will use technology to see how facial expressions of users change when they come across different types of content on the site," Independent.co.uk reported on Friday. 

The patent document also suggests that the company would also analyse those images to see how users feel and later use that information to keep users on the site for longer.

For example, if you smiled looking at one of your friends pictures, Facebook's algorithm would use that information and display more pictures of that friend in your News Feed.

"Another example included in the patent application explains that if you looked away from your screen when a video of a kitten played, Facebook would stop showing similar type of videos in your Feed," the report noted. 

Facebook applied for the patent in February 2014 and published in August 2015, but this was only recently spotted by CBInsights.

"We often seek patents for technology we never implement, and patents should not be taken as an indication of future plans,” said Facebook spokesperson told Independent.

Interestingly, a picture posted by founder Mark Zuckerberg showed that he covers the webcam and microphone on his computer. Not surprisingly, the picture went viral. At a time like this, Facebook’s patent application may only draw more criticism.

The patent also talks about a new text-messaging platform that would detect how hard you type, and use that information to attempt to work out how you feel.

However, Facebook has not put these plans into action yet, and there's no guarantee that it ever would in future.