When an adult's identity is stolen, he or she often discovers the theft in a month or so, when the next financial statement comes in.
But when it's a child who is being ripped off, it can be many years before the fraud is discovered.
"Parents have no idea that their children's identities have been stolen until they have become adults and find that their credit report says they are in debt," said Steven Toporoff, an attorney with the Federal Trade Commission's division of privacy and identity protection.
The FTC is planning to hold its first workshop on child identity theft, called "Stolen Futures," in July to raise awareness of the problem and come up with ideas on how to protect youngsters.
Parents can start now by keeping kids' personal information secure. And they can teach children not to share identifying details when surfing the Internet.
It is unclear how often thieves employ a child's Social Security number to obtain credit, get a job or start their lives over using a new identity. The FTC says 8 percent of identity theft complaints last year came from those 19 and younger, a slight increase over the year before.
"Child identity theft tends to go under-reported," Toporoff said. And 8 percent "may be just the tip of the iceberg."
A report this year by Carnegie Mellon CyLab concluded that some thieves target children.
CyLab researchers reviewed tens of thousands of cases in which personal information was compromised in data breaches and found that children were 51 times more likely to be victims of identity theft than adults. In 10 percent of the cases involving children, someone else had been using the child's Social Security number.
Children are targeted because they are likely to have unblemished credit histories. Thieves also know they probably will have years to piggyback on the child's identity before being discovered.
Often, the identity theft is uncovered only when victims are in their late teens and starting to apply for credit cards and student loans, experts say.
"There's an open market for Social Security numbers that belong to minors," said Linda Foley, founder of the Identity Theft Resource Center in San Diego. "They have a long shelf life."
Sometimes the thieves are strangers, who might sell a child's number over and over. But often the culprits are parents, grandparents and other relatives who have access to a child's information.
A man in Florida was sentenced in March to nearly three years in prison for using his son's Social Security number for more than a decade, according to the Justice Department. The father, who was in the country illegally, named his son after himself, officials say. And once the child had a Social Security number, the father was able to use it to get a job, driver's license and home loan.
Foster children are especially vulnerable, experts say, because their information is often passed around, increasing the likelihood that it can fall into the wrong hands.
Thieves can do a lot of damage before they're caught. CyLab cited a case in which eight people are suspected of opening 42 accounts and racking up more than $725,000 in debt using a 17-year-old's Social Security number.
So what can parents do to protect their children? Here are some tips:
Keep personal information private. Guard your children's Social Security number and don't give it just because a business or after-school sports program asks for it.
"Push back," said Michelle Dennedy, a privacy consultant and founder of the Identity Project website. "Be a good consumer. Ask why they need this information."
And if you must provide the information, ask how the number will be protected.
Don't carry your child's Social Security card on you, where it could be lost or stolen. And don't let your child carry it either.
The Social Security Administration will be making changes next month that officials say will help protect the integrity of the nine-digit identifier.
Ever since the agency began handing out numbers, the first three digits indicate the state where the application came from. But beginning June 25, new numbers are to be issued at random with no geographic indicator. This will make it more difficult for someone to reconstruct a Social Security number using public information.
Teach cyber safety. "We have kindergartners on computers now," Foley said. Children need to learn not to post personal information on the Internet. And they should be taught to notify parents when someone online asks for Social Security numbers or passwords.
Look for red flags. Are debt collectors calling your child? Is your 12-year-old getting credit or debt consolidation offers? Does a relative receive bills addressed to your first-grader? All these should raise suspicions and prompt you to investigate.
Check a child's report. If you suspect your child may have been a victim of fraud, contact the three major credit bureaus.