HN Explorer

Ask HN: How Facebook finds my friends given it is a new email account?

6 points by bluerail ↗ HN
I had a facebook account some time back and I deactivated it once after I had some alternatives to get in touch with friends.

A month ago I signed up for facebook with a new email account to get FB developer key.. after a week or so, I started receiving friends recommendations from facebook and it was so horrifying that it suggests my friends' profiles exactly.. This email account was new and I had only one email communication with one of my friend's official email address which is also different from his facebook connected email account.. after few days, the recommendations became pretty obvious it sent the profiles of my colleagues from my previous company... I am totally on the black here.. Any idea of how its possible or Am I missing any piece....?

PS : The previous fb account was connected through a Gmail account and this new account was opened with an Outlook account..

5 comments

[ 3.2 ms ] story [ 21.7 ms ] thread
techjuice
There are many possible ways that Facebook was able to aggregate who your friends were. Some of these are: Your history of searches, people you looked at, things you liked, your IP address, GPS location, facial picture, login patterns, people who searched for you with your new email account, sites you tried to connect to while on a page that linked back to Facebook that had the same cookie tracking information from your other account. Depending on the amount of information you made available in your previous account they could have used that along with tracking cookies or other stored data if you used your mobile device to associate your new account with your old account and friends.
bluerail
Does that mean, nothing is secret anymore?
jelos98
It never was. You just didn't realize it.
techjuice
Well the information you put on their site would only be private if you made it private. Though you set your information as private you and Facebook staff can still see this information. The system can still graph your previous account information to your new account if you have added similar or the same information which makes it easier to view any previous connections.

As some sites, they do not delete accounts but only deactivate or make them invisible as you can still reactivate your account if you wanted to https://www.facebook.com/help/212666185422169.

amarcus
FB's recommendation engine looks at the contacts shared by their users. If they see you in a friends address book, it will recommend them to you. I think it looks at name, location, email, cell etc... to make the connections.

As well as that, even though your friend is using a different email address to the one he uses to login to FB, I bet you that FB knows your friends other email and has made the connection.

Here is a fun little game to play - Create a brand new FB account using a brand new email and your actual cell number. The list of recommendations that FB will give you are people who have your cell number in their phone's contacts application. Really cool way of knowing who has your number.