Depending on your number of friends, you could have as many as seven million people seeing your Facebook profile.
That's a lot of people.
The problem is the "Friends of Friends" visibility option. With this enabled, all of your friends' friends — most likely people you don't know — can see parts of your profile.
Even the average Facebook user, assumed to have 245 friends, will be seen by over 150,000 people through "Friends of Friends."
To keep your Facebook activity contained to your friends, follow these steps: