"They should pull those Web sites down," he said. "They better know the client."
Still, Hulme said private investigators have generally proved to be more careful stewards of private data than are information brokers. His organization is beginning a lobbying campaign to ensure that any new laws don't cut off private investigators' access to data they say they need.
Keeping Social Security Numbers Safe Although Social Security numbers are used by businesses throughout the economy, privacy advocates recommend that individuals take several steps to limit the distribution of their numbers.
Several members of Congress are sponsoring new privacy legislation, including bills that would ban the sale of Social Security numbers without individuals' permission.
Private investigators are clearly worried. In Internet chat groups, they exchange information on which data brokers are still selling full Social Security numbers, while bemoaning how they are being punished for the security lapses of the brokers.
For their part, ChoicePoint and LexisNexis say they are "re-credentialing" all non-government clients. At ChoicePoint, those who use the Internet to request information were greeted with a pop-up notice indicating that privileges might be restored after the certification process was complete.
ChoicePoint declined to provide an executive for an interview. Spokeswoman Kristen McCaughan said the company plans to give full access only to government or law-enforcement agencies, banks and insurance companies. She declined to say how many of its customers, including private investigators, would end up with restricted access.
McCaughan said the company sells data to fewer than 15 other brokers or re-sellers, and that their access will now be subject to stricter guidelines.
A LexisNexis spokesman said clients downgraded to restricted access included law firms, media and private investigators.
The financial services industry argues that it has steadily reduced its reliance on the Social Security number for several years, but that the number's use has benefits for consumers.
Nessa Feddis, senior federal counsel of the American Bankers Association, said that with so many numbers consumers already must remember, using Social Security numbers to verify accounts makes sense.
If a credit-card is lost or stolen, she said, a consumer can quickly report the missing card to a bank by knowing his or her Social Security number. If the only accepted identifier was a separate account number, she said, the person would have to wait until he or she could get to a credit-card statement at home.
Privacy experts argue that at the very least, institutions should employ multiple test questions when people call in, rather than just the Social Security number. And they point out that if the number is compromised, it is hard to limit the damage because new numbers are almost never issued.
"The current system has the worst of all worlds," Solove said. "Anyone can easily find it [the Social Security number] out . . . It's used everywhere, and it's really hard to change if it falls in the wrong hands. How could you come up with a worse system?"