HTTP over SSL (HTTPS) is used to create an encrypted channel between the client and server to protect the data transferred between them; also, it allows the client to validate the authenticity of the server.

Three years ago, most websites were running in HTTP and would allow firewalls to understand and inspect passing traffic. Nowadays, most websites tend to use HTTPS by default, such as Google and Facebook, which will shift the session to HTTPS even if it was initiated using HTTP. Using HTTPS results in firewalls being unable to understand or inspect the passing traffic, which affects the firewall's functionality as some of the blocked sites could be accessed by using HTTPS. Allowing firewalls to understand the HTTPS traffic became a necessity.