Unknown contacts appeared out of thin air My contact list op my iPhone 5s suddenly shows hundreds of contacts for people that I do not know with full contact info. I have synced with Facebook and have LinkedIn and Exchange installed, but these contacts are not part of my "friends". Has anyone experienced the same issue? What can I do?
There are many possibility:

1: Facebook sync with your contact info, as I know, Facebook will suggest people you may know to you.

2: Are you using a same Apple ID with your families or friends? Contacts will sync to your other device with same Apple ID.

3: Are you using other's SIM card? SIM card store contact inside the micro chip!!

4: Your Apple ID have been hacked.....change your password immediately and never tell others your ID and password.