As you are strolling through malls and department stores while Mariah Carey’s “All I Want for Christmas Is You” is blaring through the loudspeakers, there are insidious people seeking to swipe gifts intended for your loved ones and use them for their own purposes.

It’s called the “gift card draining” scam, and far too many people are being caught unawares as they go about their Christmas shopping.

State and local governments, law enforcement officials and consumer advocate groups are warning holiday shoppers this year to be aware of a popular gift card scam that involves tampering before the card is purchased and emptied after activated or used.

“Gift card draining” involves criminals recording numbers and PINs from unpurchased gift cards, then placing them back in the packaging. These thieves then wait until the card is purchased and activated – finding that information online – and use the card until the balance is depleted, leaving the buyer with a worthless gift card.

What makes these even more troubling is that the crooks perpetrating this scam know that the recipients of the gift cards are unlikely to try spending them until after Christmas Day, which gives them plenty of time to steal the money loaded onto the cards. Then, when the recipient goes to use the card, they are met with an unwelcome surprise.

Some of the Daily Mail’s readers contacted the news outlet to tell their stories about being conned in this fashion. One individual recounted being embarrassed after a $100 gift card was drained of its value. A New Yorker discovered $650 missing from two $500 gift cards. Apparently, the money was spent on Amazon purchases. He later noticed glue dots on the packaging, which is a common clue that a gift card has been tampered with.

Fortunately, there are ways to guard against falling victim to these schemes.

Cops are warning shoppers to check for any signs that a card has been meddled with - such as scratches or scuff marks or parts of the card missing - before purchasing.

This is because - to get the numbers -  the crooks typically will have scratched off the silver security foil. They then replace this with a near identical sticker or more foil, which is sold online on sites like Alibaba.

Damage to the card or foil is a tell-tale sign that fraudsters have obtained the card's details - putting any funds added to the card at risk of being stolen.

It is also a good idea to hold on to the receipt after purchasing the gift card. This will make it easier to report the fraud if it occurs.

Unfortunately, there are many different methods criminals use to scam people out of their hard-earned money – especially during the Christmas season. It seems that for every person looking for presents for their loved ones, there is someone out there cooking up schemes to separate these people from their money. Gift card draining has become more prevalent due to the increase in people giving them as gifts. Hopefully, more people will not have to learn about the scam the hard way.