The NIS asserted the need to tap Gmail when applying to a court of law for permission to also use communication restriction measures [packet tapping]. The court, too, accepted the NIS's request at the time and granted permission for packet tapping.
Unlike normal communication tapping methods, packet tapping is a technology that allows a real-time view of all content coming and going via the Internet. It opens all packets of a designated user that are transmitted via the Internet. This was impossible in the early days of the Internet, but monitoring and vetting of desired information only from among huge amounts of packet information became possible with the development of "deep packet inspection" technology. Deep packet inspection technology is used not only for censorship, but also in marketing such as custom advertising on Gmail and Facebook.