The data could be abused by the government or the private company that keeps it, the advocates contend. They also say there is no need for the information to include Social Security numbers, which could be used to steal someone's identity.
The military says the information will help steer it to potential recruits. Officials said the Social Security numbers are scrambled to prevent abuse and that the database only has been used for recruiting purposes.
The issue has surfaced as the regular Army — and the reserves of all four military branches — are having difficulty attracting recruits.
"The program is very important because it helps the recruiters be more effective to target qualified candidates for specific missions," a Defense Department spokeswoman, Air Force Lt. Col. Ellen Krenke, said Thursday.
The Pentagon's Joint Advertising, Market Research and Studies Group has overseen the data since 2003, when it took over several recruiting databases managed separately by the military services.
The military says it collects the data itself. It has hired one company, Mullen, to manage the information. Mullen hired a subcontractor, BeNow, of Wakefield, Mass., to process the data.
Privacy advocates learned of the database only recently after the military, as required by law, put a notice in the Federal Register, a federal government publication, that it keeps such information.
David Chu, undersecretary of defense for personnel, said it was a "fair complaint" that the Pentagon should have given notice in 2003 instead of now.
The privacy group's concerns were reported in The Washington Post on Thursday.
According to the Federal Register notice, the data includes high school students age 16 to 18, college students, and people who have registered with the Selective Service, which would manage a military draft if it were reinstituted.
American men age 18 to 25 are required to register with Selective Service and provide their Social Security number.
The information kept on each person includes name, gender, address, birthday and, if available, the Social Security number, e-mail address, ethnicity, telephone number, high school, college, graduation dates, grade-point average, education level and military test scores, the notice in the register said.