(WTAJ/NEXSTAR) — It’s the latest trick scammers are using to steal your money via gift cards and you might not know until it’s too late: it’s called “card draining.”

Police in eastern Pennsylvania have put out a warning to all Americans heading into the holiday season after 100 different gift cards, including Visa and Apple cards, were reportedly drained at a local grocery store. But the problem has been seen all across the U.S., including multiple incidents in Colorado this summer.

What is card draining?

Card draining is just that. They drain the gift card. But how do they drain a gift card that isn’t activated and has no money on it?

Short answer: They don’t.

This scam involves the culprits taking cards off displays and carefully getting the information from the back of the gift card before putting them back. From there, they wait. These scammers use a little patience and wait for these cards to be activated and money put on them — once they see it’s active, they’ll use and drain it.

What to look out for

You should carefully check all gift card packages before you buy them: Is it already opened? Does it look tampered with? One example from law enforcement is the Visa Vanilla gift card package. They said it doesn’t need much tampering to reveal the pin code and the package doesn’t even need to be opened to do so.

If a gift card looks tampered with, opened, or has the numbers on the back already scratched off and revealed, you should take it to a cashier at whichever store you’re at and alert them.

You should not put it back on the display for someone else to get scammed.

The scam has been around for years but has continued building in popularity, since it’s so easy to do. Back in 2016, security analyst Thomas Ciccone told NBC News that two ways to increase safety is to purchase gift cards directly from a retailer’s website, where numbers are randomly generated.

Additionally, Ciccone said, if possible, purchase gift cards with a credit card since many credit card companies offer purchase protections that banks don’t.

Remember, even with technology constantly and rapidly evolving, scammers’s tactics are evolving alongside it.