Internet access itself is limited to a handful of elite users and scientists. Instead, North Korea has a walled garden intranet system called Kwangmyong, which is maintained and monitored by the Korea Computer Center. Its content is limited to state media, chat services, message boards, an e-mail service and an estimated 1,000–5,500 websites. Computers employ the Red Star OS, an operating system derived from Linux, with a user shell visually similar to that of OS X. On 19 September 2016, a TLDR project noticed the North Korean Internet DNS data and top-level domain was left open which allowed global DNS zone transfers. A dump of the data discovered was shared on GitHub.