How to track a phone?

How can you track someones phone number who is hacking your facebook from their phone?

• Ok long story short. So a friend of mine got his facebook account hacked. He changed his password 3 times but he still keeps getting hacked, the person hacking his facebook keeps messaging me telling me to break up with my girlfriend or else I am going to get my *** kicked by a group of people (I'm really not scared, I just want to find out who is saying this crap) I don't know who is hacking his facebook, however the person who hacked his facebook is using a mobile phone because it says mobile on my computer. I was wondering if there is any way to somehow view the phone number of the phone that that person is using to log into my friends facebook so I can call the number and figure out who it is.

• Answer:

  your best bet would be to show the police. Unless you are intimately familiar with how password-sniffing, keylogging, and firewalls work, then your best bet is to simply show the police. Afterwards, you probably want to reformat your computer.