An unfamiliar face catches your eye as you scroll down your timeline – someone you may know, according to Facebook.

Yet, on closer inspection you have no mutual acquaintances and there are no obvious links as to why this person has been suggested as a ‘friend’.

Exactly why did Facebook recommend this person to you? What information did it use to do so? And how can you limit the information available to it, should you so wish?

This week we are publishing a series of articles throwing a spotlight on the social media giant’s use of data.

We began with how it targets you via tagging and location then looked at the accessing of phone contacts and email accounts.

Today we focus on search history - something you may think isn't recorded, but in fact is.

READ MORE: How Man City are using social media to understand fans

A feature of business networking site LinkedIn is that it reveals who has viewed your profile, yet Facebook does not.

However, people you have searched for and those who have searched for you then become suggestions of ‘people you may know’.

This means the information on any searches you make is recorded and used to personalise your Facebook account.

If there seem to be no obvious reasons a person may have been suggested to you then the chances are they may have searched for your profile previously.

Facebook doesn’t give specifics on this, but its terms and conditions say it collects information about the type of content you view, along with the frequency and duration of the activity.

It also states that it collects information about the people and groups you are connected with and how you communicate with them. 

So if you think checking someone out on Facebook is risk-free, think again - that is, if you don't want them to know

Facebook failed to respond to two separate requests for comment.

Tomorrow: Focus on external apps