WASHINGTON -- The next time you're asked to give out your Social Security number, stop. You may be taking a terrible chance with your privacy -- and your wallet.
By using your number, clever crooks can dip into your bank account, take out a credit card in your name, get hold of your government benefits or browse through your college records or financial investments.
That's why Marc Greidinger refused to supply his Social Security number when he tried to register to vote in Stafford County, Va., in July 1991 -- even though it cost him his right to vote.
"It's been my practice not to give my number out, unless there is a good reason for asking for it," the 30-year-old lawyer said. "It can be used to rip me off or violate my privacy."
As a test, Mr. Greidinger had a friend dial an 800 number at the government-sponsored Student Loan Marketing Association (Sallie Mae) in Washington.
"He entered my Social Security number into the telephone and was able to get access to my files. He found out how much I owed, and when I made my last payment. He even changed some data in my file."
The friend also got Mr. Greidinger's academic transcripts at the University of Maryland by writing to the admissions office, using the Social Security number as verification.
"He passed himself off as me," Mr. Greidinger said.
Mr. Greidinger sued the Stafford County vote registrar after he was prevented from registering, and last summer a federal appeals court unanimously ruled in his favor.
"The harm that can be inflicted from the disclosure of a Social Security number to an unscrupulous individual is alarming and potentially financially ruinous," the court said.
Since then, Virginia still collects the numbers as a check against vote fraud, but no longer makes them available to the public as it used to.
The Greidinger case was another round in a 50-year struggle between those who want to use Social Security numbers as a personal identifier for everything from law enforcement to check cashing -- and those who view its widespread use as a serious threat to privacy.
The battle is getting more intense as Congress and the Clinton administration debate whether to use Social Security numbers to identify people under a new national health care system.
"Due to its widespread use for both public and private purposes, the use of the Social Security number will jeopardize the privacy and security of personal health information maintained under the act," warned Janlori Goldman, director of the American Civil Liberty Union's Privacy and Technology Project, during recent Senate testimony.
Phil Gambino, a spokesman for the Social Security Administration, said the agency had no power to prevent the abuse of the number by private individuals or companies.
"You should be judicious about giving it out, but it's up to you to decide," Mr. Gambino said. "Sometimes you can't get the service you want if you don't give your number."
The vulnerability of Social Security numbers was dramatized in a recent scandal involving Social Security employees who sold information to Nationwide Electronic Tracking, a so-called "information broker" advertising "instant access to confidential data . . . 24 hours a day, 7 days a week."
The company bought the names, dates of birth, salaries and the past and present employers of people listed in the Social Security Administration's computer files, said Larry Morey, deputy inspector general of the Department of Health and Human Services. It paid $25 a head for the data and resold it for $300 or more to other companies, who wanted the information to locate people or to make decisions about hiring, firing or lending.
There are many other ways in which Social Security numbers can be obtained. At some universities, for example, students' names and numbers are posted openly on bulletin boards along with their grades.
In addition, Social Security numbers are easy to fake and hard to authenticate.
"There is no way to verify the accuracy of existing numbers or that the number holder is who he or she claims to be," Mr. Goldman of the the ACLU said.