A new generation of skimmers that wirelessly transmit stolen data is stymying authorities and causing anxiety among credit unions and other card issuers anticipating upcoming EMV liability shifts at ATMs and gas pumps.

The skimmers use Bluetooth — a technology that lets devices communicate wirelessly when they're within about 30 feet of each other — and they're keeping people like Wisconsin Trade and Consumer Protection Division Administrator Frank Frassetto up at night.

Among other things, Frassetto's team enforces consumer protection laws, regulates business practices and tests gas pumps annually in the state. He said it got word last spring of wireless skimmers at Michigan and California gas stations; later, there was an incident in the Southeast. By August, they were in his backyard — an equipment technician doing routine maintenance discovered one at a gas station in Madison.