You will definitely want to track, who is using your Facebook account hiddenly. Suppose somebody is opening your Facebook account from an unknown mobile device then it will be a great surprise for you. You will definitely want to know all of your unwanted account activities. OK relax for a while. Today I will tell you how to track them.
Login to your Facebook account and click on account settings as shown in the following figure.
In the account settings, click on the link security as shown in the following figure.
Click on the link Active Sessions as shown in the below diagram.
If any unknown session is there then quickly end that session by clicking on the link End Activity.