Law enforcement officials are warning shoppers to pay close attention to the payment terminal the next time they are in a checkout line.Video from a Walmart in Erwin, New York, nearly 80 miles west of Binghamton, shows three people working together to attach a credit card skimmer to the payment terminal in a checkout line. The process took less than 30 seconds and the trio pulled it off in front of the cashier, who did not notice what had happened.Cases of skimming have happened at 16 different Walmart stores across New York and Maine, according to authorities.“Unfortunately, there’s going to be a lot of victims involved in this,” said Trooper Lynnea Crane, a public information officer for the New York State Police.Skimming is when thieves attach a device to a payment terminal that oftentimes goes unnoticed by shoppers and store employees. Those devices can collect credit or debit card data, as well as a personal identification number.The FBI says skimming costs consumers more than $1 billion each year."Technology makes things sometimes safer and better. They also make it easier for criminals, and they're always working on the next front," said Brad Leonard, assistant to the special agent in charge of the Miami field office of the U.S. Secret Service. "We stop them one way and they find another way to do it."In a statement, Walmart said it is reviewing protocols and adding enhanced security measures to better protect in-store transactions."Providing customers with a safe shopping experience is a top priority," Walmart said in its statement.Authorities say the best tip to protect against skimming is for shoppers to make sure they're covering up the number pad on a payment terminal as they enter their PIN.In addition, shoppers should try and take a look at different payment terminals to see if they look the same as the one they are about to use. If part of the payment terminal looks loose, crooked or damaged, shoppers should use a different machine.Related story: