WEB SITES REMOVE DOCUMENTS
U.S. government departments and agencies also have been stripping a wide range of documents from Web sites in recent days because of perceived threats to such critical systems as pipelines, water supply stations and power plants. 
The Nuclear Regulatory Commission, for instance, took down its entire Web site Thursday to review its content for "information that might be useful to adversaries," said spokeswoman Rosetta Virgilio. 
She said many other federal agencies also appeared to be in the process of removing such information from their sites. 
The Transportation Department's Bureau of Transportation Statistics has cut off public access to databases used for mapping because of stepped-up concern about U.S. transportation infrastructure. 
The Environmental Protection Agency has dismantled its risk-management Web site, which contains general information about emergency plans and chemicals used at 15,000 sites nationwide.