Kansas City, Mo. ? The latest form of identity theft doesn’t depend on stealing your Social Security number. Now thieves are targeting your kid’s number long before the little one even has a bank account.

Hundreds of online businesses are using computers to find dormant Social Security numbers — usually those assigned to children who don’t use them — then selling those numbers under another name to help people establish phony credit and run up huge debts they will never pay off.

Authorities say the scheme could pose a new threat to the nation’s credit system. Because the numbers exist in a legal gray area, federal investigators have not figured out a way to prosecute the people involved.

“If people are obtaining enough credit by fraud, we’re back to another financial collapse,” said Linda Marshall, an assistant U.S. attorney in Kansas City. “We tend to talk about it as the next wave.”

The sellers get around the law by not referring to Social Security numbers. Instead, just as someone might pay for an escort service instead of a prostitute, they refer to CPNs — for credit profile, credit protection or credit privacy numbers.

Julia Jensen, an FBI agent in Kansas City, discovered the scheme while investigating a mortgage-fraud case. She has given presentations to lenders across the Kansas City area to show them how easy it is to create a false credit score using these numbers.

“The back door is wide open,” she said. “We’re trying to get lenders to understand the risks.”

It’s not clear how widespread the fraud is, mostly because the scheme is difficult to detect and practiced by fly-by-night businesses.

But the deception is emerging as millions of Americans watch their credit scores sink to new lows. Figures from April show that 25.5 percent of consumers — nearly 43.4 million people — now have a credit score of 599 or below, marking them as poor risks for lenders. They will have trouble getting credit cards, auto loans or mortgages under the tighter lending standards banks now use.

The scheme works like this:

Online companies use computers and publicly available information to find random Social Security numbers. The numbers are run through public databases to determine whether anyone is using them to obtain credit. If not, they are offered for sale for a few hundred to several thousand dollars.

Because the numbers often come from young children who have no money of their own, they carry no spending history and offer a chance to open a new, unblemished line of credit. People who buy the numbers can then quickly build their credit rating in a process called “piggybacking,” which involves linking to someone else’s credit file.

Many of the businesses selling the numbers promise to raise customers’ credit scores to 700 or 800 within six months.

If they default on their payments, and the credit is withdrawn, the same people can simply buy another number and start the process again, causing a steep spiral of debt that could conceivably go on for years before creditors discover the fraud.

Jensen compared the businesses that sell the numbers to drug dealers.

“There’s good stuff and bad stuff,” she said. “Bad stuff is a dead person’s Social Security number. High-quality is buying a number the service has checked to make sure no one else is using it.”

Credit bureaus can quickly identify applications that use numbers taken from dead people by consulting the Social Security Administration’s death index.

Social Security numbers follow a logical pattern that includes a person’s age and where he or she lived when the number was issued. Because the system is somewhat predictable, sellers can make educated guesses and find unused numbers using trial and error.

Experts say the fraud will be difficult to stop because it’s so easily concealed and targets such vulnerable people. Other than checking with the credit bureaus to see whether there is a credit file associated with your child’s Social Security number, spokesmen at FICO, the Social Security Administration and the FTC said there are no specific tools for safeguarding the number.