ORLANDO, Fla. -

The anti-fraud stickers are red with black lettering and read: “Security seal. 7-11 Cares about your ID. Please Report Immediately if 'VOID OPEN' appears.”

If the tape is cut, torn, removed, or tampered with in any way, it begins to change color and eventually reveals the words “VOID OPEN.”

At 7-Eleven gas station pumps across Central Florida, the lock box that contains the credit card reader is sealed with the sticker to alert customers if it has been opened illegally.

Con artists often break into the boxes to install a skimmer -- an electronic device that stores credit card numbers when credit cards are inserted into the card reader.

A 7-Eleven spokesperson told Local 6 that every store is instructed to keep the stickers on hand and check the integrity of the sticker daily.

“Store personnel need to break seals each time they have to change the customer-receipt tape and then replace with a new seal,” said Margaret Chabris, director of corporate communications at 7-Eleven.

Over the past few years local law enforcement has confiscated skimmers at bank ATMs, grocery stores and gas stations.

"I used to work at the fraud department for a bank and the number one cause would be gas stations,” said Kevin Figueroa. “Yes, that was a very popular call."

Figueroa told Local 6 that he inspects the sticker every time he fills up and even pulls on the credit card reader to see if it's loose, in case the skimmer was installed over the credit card reader, not inside the lock box.

Pictures of skimming devices from law enforcement show that some skimmers are small enough to be placed on top of the card reader, so a customer inserts his or her card into the con artist's skimming device and not into the actual gas pump card reader.

But Local 6 discovered that many drivers do not inspect the stickers and some don't even realize they're there.

“I probably would've filled this with gas and not even known about it at all,” said Sean Cassidy, who fills up at the 7-Eleven at the corner of Lee Vista Boulevard and Narcoosee Road twice a week.

Figueroa said the sticker is effective only if a customer knows to look for it.

A 7-Eleven employee told Local 6 the stickers are working.

“We have not had any incidents so far this year in the Orlando area,” said Chabris. “We at 7-Eleven take the matter of gasoline-pump skimmer devices very seriously. That is why we have procedures in place to guard against fraudulent activity. Also, we are working on other solutions that are confidential at this time.”