HANOI—The Internet poses a challenge for authoritarian regimes around the world. But Vietnam's leaders think they have figured out a new way to tame it—by launching their own, Communist-friendly answer to popular social-networking sites like Facebook. It's called go.vn, and state-owned Vietnam Multimedia Corp. launched a trial version on revolutionary hero Ho Chi Minh's birthday, May 19. A full version is due to go up at the end of the year. Many of its features will be familiar to anybody versed in tagging, poking and defriending: People can post photos, link to friends and ping messages back and forth online. The catch is that users have to submit their full names and government-issued identity numbers before they can access the site. Security services monitor websites in Vietnam, whose authoritarian, one-party dictatorship treats dissidents ruthlessly.