Many people use protocols like http/ftp to transfer the data, but sans of proper knowledge. How does it work? Whether it is safely reaching the desired destination, or it is being public, or someone illegally accessing it with out your consent.

Ever since man has learnt to interconnect his private network with other network, his second thought is how exchange only authorized data. Unknowingly many data gets allowed to be exchanged- sometimes intentionally data is assessed by others from one's private network. This is the called hacking. As the technology of exchanging data between personal networks increases the technology of unauthorized data assessing develops, man then thinks of a technology to prevent the unauthorized data accessing. This technology then took the shape of software- it is christened as firewall now.