1-Go to your facebook timeline page.
2-Click on the profile pictures box, just at the left side of your timeline cover.
3-Next to the "Share with" option, click on the drop-down list and select whom can see your picture: select whom can see your profile picture. You can either choose friends or only me, you can also custom the photo's privacy for only specific persons to see it, or prevent others from viewing it, however if you want to make your profile photo private from strangers selectFriendsonly. Only your friends now can see your profile photos. Now your facebook profile pictures are well protected from strangers, If you want to change these settings back again, follow the same process and re-set the privacy for public. that's all. I hope this article was helpful for you.