"To the naked eye you can't see that there's anything there," said Bayer-Broring. "But when you use the spot filter that's available to us, you are able to see that actually there was prior data that was on this document that has been rinsed off."
Many business owners, especially those in the agriculture and the construction trades, say they are at a loss to tell real IDs from fake ones, and as a result, have no way of knowing if they are hiring legal or illegal workers.
"If an applicant for a job comes in and brings you three valid forms of identification, they look real, they look valid to you, you can't go much beyond that without putting yourself at risk of discrimination," said National Association of Home Builders CEO Jerry Howard.
The problem, say government investigators, is that this black market industry has millions of customers, just waiting for the opportunity to buy their way into the system, even if it is illegal.