PARIS — All over the world, Internet users entertain romantic delusions about cyberspace. To most of us Web surfers, the Internet provides a false sense of complete freedom, power and anonymity.

Every once in a while, of course, unsolicited messages and ads that happen to be mysteriously related to our most intimate habits intrude. They remind us that we Internet users are, indeed, under constant virtual surveillance.

When the watchers have only commercial motives, such "spam" feels like a minor violation. But in China or Russia, the Internet is patrolled not by unsolicited peddlers, but by the police.