‘Periscope’ Skimmers are installed entirely inside an ATM and are designed to steal your debit card’s or credit card’s numbers. Because they are installed inside the ATM, you will not see any clue there is a skimmer installed when you use the ATM. Crooks who use this type of device eventually will want to capture your PIN so they can later drain your debit account at another ATM.
The US Secret Service task force warned that the devices may have the capability to remain powered within the ATM for up to 14 days and can store up to 32,000 card numbers before exhausting the skimmer’s battery strength and data storage capacity.
You can read more on at Krebs on Security at https://goo.gl/Lr9TsX.