BEFORE September 11, you could have visited the Federation of American Scientists' website for diagrams and photos of US intelligence facilities.
You could have gone to another website and learned of gatherings at North Dakota's Minot Air Force Base. And you could have gone online and ordered maps of military installations.
Concerned they could be aiding terrorists, some US Government and private websites have decided to stop sharing quite so much potentially sensitive data.
Such self-censorship would not prevent terrorists from turning to libraries or even other websites for information that could be useful in attacks.
"But that is not a justification for publishing it in easily accessible ways. Let them work for it," said Steven Aftergood, senior research analyst at the scientists' group.
The private organisation removed from the web its research containing locations, building layouts and aerial images of intelligence offices, some unacknowledged by the US government. Also removed were details on nuclear sites abroad.
Minot removed clues about where personnel may be gathering, including schedules of activities and locations of military housing units.
The National Imagery and Mapping Agency suspended online and offline sales of maps of military installations as well as its highest-resolution maps of other US locations.
The US Office of Pipeline Safety now restricts its mapping software and pipeline data to industry and government officials, while the Environmental Protection Agency removed information on chemical plants and their emergency response plans.
"People have a right to know what kinds of risks there are, but unfortunately terrorists are people, too," said Jim Makris, the EPA's emergency coordinator.
The reports were still available in EPA reading rooms, but Mr Makris said identification was required.
News source: The Associated Press