28b3984c_mal_and_Informal_Communication__Informal_communication
[SL] 3 [Points of Difference] Secrecy [Formal communication] Such communication is not free and open to all. So secrecy is maintained here. [Informal communication] 
It is free and open to all, so it is very difficult to maintain secrecy here.
Difference Between Formal and Informal Communication
Informal communication