Israel insists that the identity of its secret service chief is still classified information, even though a hacker has posted his name and address on the Internet. When the new head of the service, called the Shin Bet, took over on Mar. 1, an anonymous poster, or prankster, urged Internet users worldwide to send him congratulatory E-mail. Israeli newspapers reported the story, only to have the country's military censor delete the name and address. (Israeli media are allowed to refer to him only as "C.") Today, the censor, Brig. Gen. Yitzhak Shani, announced that he would continue banning the name from publication in Israel. But the country's judicial system may soon rule otherwise, and, as the Haaretz newspaper of Jerusalem put it: "Whoever put out the name on the Internet . . . transmitted a warning that the world is changing."