Firstly you need equipment that is networkable, such as Dreambox and similar linux based satellite products. These receivers have ethernet connection in the same way as computers do, and have ability to use developed software to send and receive information.
Over the years of development many versions of software have evolved and names such as Newcs, Cccam, Mgcamd, Gbox, Newcamd and others have gained popularity due to their ability to network-share. Legal practical use has allowed the subject to expand and even top brand names like PACE, Amstrad, etc, now use the idea to develop new hardware for the future. Legal benefit to networking is you are able to pay for an encrypted package and then watch with a receiver of your choice in your own home and no longer need to keep taking the card in and out of the slot and forgetting where it is etc…