Hijacking (man-in-the-middle attack)
Hijacking is an attack technique where man-in-the-middle takes advantage of the way headers are constructed in a weakness in the TCP/IP protocol stack. Hijackers perform hijacking by actively monitoring capturing, and controlling your communication transparently when you are communicating with another person. The attacker may re-route a data exchange and while your computers are communicating at low levels of the network layer, they might not be able to find with whom they are exchanging data. Man-in-middle attacks takes the advantage of this technique as the person with whom you communicate will think that it is you (actual user) who has sent a message whereas the fact is, it is the hacker who actively responding on your behalf using your identity. So if you find anything unusual while having conversation with your friend of receiving any message from the unauthorized contact, avoid any kind of communication as this may be either a hacking attempt or hacker.