Much of the crime hinges on member misperceptions about how the check-clearing process works, the BBB noted.

"For fraudsters, the possibilities are almost endless in how they exploit people's erroneous belief that having the money credited to a checking account means the check is good," it warned.

Secret shoppers

The most common check fraud scam involves mystery shopper or secret shopper schemes, it said. Those schemes tend to contact victims by mail, offer jobs as mystery shoppers and enclose a check to deposit into their own checking accounts. The victims are then told to shop, wire part of the money back to the fraudsters and allowed to "keep" the rest.

There is a real mystery shopping industry, but legitimate companies typically don't send money in advance to shoppers, the BBB warned.

Overpayments and collection scams

In these scams, victims selling items online receive a legitimate-looking check for more than the sale price. The buyer asks the victim to refund the difference via a wire transfer.

Fraudsters also frequently contact lawyers for help dealing with a business they say owes them money. The criminal tells the lawyer than if he or she gets the money from the business, they can earn a fee. The lawyer contacts the debtor business, which is a co-conspirator in the scam and sends a fake check to the law firm. The law firm deposits the check and wires money to the fraudster.

Shrink wrap and nannies

"BBB receives many complaints from victims who are approached via email or social media to 'shrink wrap' their cars with advertisements for energy drinks, beer or other products in exchange for a monthly payment, often around $200 per month. Fraudsters tell victims that companies are happy to pay for this type of advertising," the agency said. Victims receive fake checks and then wire their own money to another company that will allegedly wrap their cars with advertising.

Another tactic is to advertise jobs for nannies or other caregivers, then send fake checks to the victims they "hire." They tell the victims to deposit the checks, then wire money to a second co-conspirator company to purchase a wheelchair or other equipment needed for the "job."

Finding the criminals

Check fraud is a global issue, according to the study. Though it often starts internationally, several steps are required to make the fraud work.

"Someone must create the checks or receive them in the U.S. or Canada," the BBB explained. "Then they must be mailed to potential victims. Finally, someone must collect the money sent by fraud victims. These steps may be undertaken by fraudsters in the U.S., but also may be the work of money mules or other co-conspirators physically in the U.S. or Canada. In short, those engaging in this fraud are very organized, and may have a variety of conspirators that make them successful. This suggests that there could be organized crime groups operating worldwide to conduct fraud."

Though wire transfers are integral components of many fraud schemes, fraudsters are shifting toward having victims buy gift cards, the BBB noted.

"They often ask victims to buy the cards, scratch-off to reveal the security code on the back, take a picture of those numbers, and text or email that photo. With these numbers the fraudsters can quickly cash out the gift cards. There is apparently a large worldwide underground market trading in gift cards," it explained.

Prevention tactics

Credit unions and banks can help prevent check fraud by reminding members that crediting money to their accounts does not mean a check has cleared or is legitimate, the BBB warned. It also advised credit unions and banks to look for these red flags often associated with fake checks:

• Missing addresses and phone numbers for out-of-state checks over $1,000.
• Shiny MICR numbers or no MICR numbers.
• Sudden changes in member deposit behavior or frequency.
• Frequent questions from the member about when the check will clear or the money will be available.
• Online deposits from IP addresses not associated with the member.

Simply talking to members also can crack a case open, the BBB added.

"When customers have deposited a check and ask to withdraw it in cash, simply asking nicely what the customer may do with the money may produce a response indicating that someone thinks they have won a lottery or sweepstakes," it said. "Most people are willing to engage, especially when it is clear that the teller is honestly trying to help. For example, the teller may ask why, if someone has won a lottery, the check is from a tire company."