Graham Cluley of security firm Sophos said that Twitter should offer extra security measures to prevent these sorts of incidents, which otherwise will continue to occur, or even accelerate. Since it is all done online, it is very difficult for the particular partner to be aware what is going on. " The call high quality is very excellent and could be adjusted to make it louder, Bluetooth works well and basic text messaging is very easy to access and use. Facebook is the largest social network with over 600 million users in the world. Foreign governments, terrorists and a "hacking collective" called Lulz - Sec have been accused.