Here is an email sent by a top Congressional security official to staffers on Capitol Hill about the threat and how people should deal with it.
Potential Threats Coinciding with the 10th Anniversary of the September 11 Attacks
Last night’s announcement concerning U.S. officials possessing “specific, credible but unconfirmed” information (which is, admittedly, rather confusing) about a potential al Qaeda threat against the United States coinciding with the 10th anniversary of the September 11 terrorist attacks was well-intentioned, perhaps helpful, but not very well-coordinated. In the anti-terrorism business, the push and pull of evaluating intelligence and when to openly share what is known or suspected is challenging; the alternatives are rarely black and white. All that said, whenever there is information we have which will make you safer, we will share it.