“This database is, in a sense, worse than a watch list,” he said. “At least in the watch-list scenario, there’s some reason why the name got on the list. Here, the only thing a person does to come to the attention of DHS is to lawfully cross the border. The theory of this data collection is: Track everyone — just in case.”

Under the system, officials record name, birth date, gender, date and time of crossing, and a photo, where available, for U.S. travelers returning to the country by land, sea or air. The same information is gathered about foreign travelers, but it is held for 75 years.

DHS and other agencies are amassing more and more data that they subject to sophisticated analysis. A customs document issued last month stated that the agency does not perform data mining on border crossings to glean relationships and patterns that could signify a terrorist or law enforcement threat. But the Federal Register notice states that information may be shared with federal, state and local governments to test “new technology and systems designed to enhance border security or identify other violations of law.” And the Homeland Security Act establishing the department calls for the development of data-mining tools to further the department’s objectives.

That raises concerns, privacy advocates say, that analyses can be undertaken that could implicate innocent people if appropriate safeguards are not used.

The border information system will link to a new database, the Non-Federal Entity Data System, which is being set up to hold personal information about all drivers in a state’s database. States that do not agree to allow customs to have such large amounts of information may allow the agency to query their databases in real time for information on a traveler.

Because of privacy concerns, Washington state earlier this year opted for the queries-only approach. The Canadian government made the same decision. “There was absolutely no way they should have the entire database,” said Ann Cavoukian, Ontario’s privacy commissioner, who learned about the Canadian government’s decision in April.

“Once you have data in a database you don’t need, it lends itself to unauthorized use,” she said. “You have no idea of the data creep.”

Vermont opted to allow access to its driver’s licenses because the state could not guarantee the “nanoseconds” response time DHS required, said Bonnie L. Rutledge, the state’s commissioner of motor vehicles. She said drivers are informed up front of the data sharing.

“A person opts to go over the border, their information is going to be collected and held anyway,” she said. “If you don’t want to go over the border, you don’t have to.”

The notice states that the government may share border records with federal, state, local, tribal or foreign government agencies in cases where customs believes the information would assist enforcement of civil or criminal laws or regulations, or if the information is relevant to a hiring decision.

They may be shared with a court or attorney in civil litigation, which could include divorce cases; with federal contractors or consultants “to accomplish an agency function related to this system of records”; with federal and foreign intelligence or counterterrorism agencies if there is a threat to national or international security or to assist in anti-terrorism efforts; or with the news media and the public “when there exists a legitimate public interest in the disclosure of the information.”

Homeland Security is proposing to exempt the database from some provisions of the 1974 Privacy Act, including the right of a citizen to know whether a law enforcement or intelligence agency has requested his or her records and the right to sue for access and correction in those disclosures.

A traveler may, however, request access to records based on documents he or she presented at the border.

The notice is posted at the Government Printing Office’s Web site.