To protect your debit card from being scanned you can use RFID blocking sleeves or RFID blocking wallets.
Also be cautious about card readers at gas pumps, ATMs and other places and cover your PIN number when entering the PIN number.
You should also enable transaction alerts and use a digital wallet when you can do so, and you should always report any suspicious activity immediately.
If you can when buying gas with your debit card or credit card you should go inside and pay to avoid the potential of a card skimmer which can more easily be placed on the gas pumps.
RFID blocking wallets and RFID blocking sleeves are designed with a material that blocks the radio waves that are used by RFID scanners and prevents unauthorized reading of your debit card or credit card's information.
Also if you have multile debit cards or credit cards you should stack them together and also consider keeping your drivers license in front of it in your wallet to help further block the RFID scanners.
And keep your wallet in your front pocket, which can also deter pickpockets and make it harder for scanners to access your debit cards or credit cards.
Before using any ATM machines or card readers you should examine the card readers for any signs of tampering like loose parts, different colors or anything else that looks unusual.
And pay attention to your surroundings when using ATM machines, especially in isolated areas or public areas and consider the use of an ATM that is inside of a bank or other secure location.
When you enter your PIN you should also use your hand to shield the keypad from potential cameras.
Also avoid using your credit card or debit card on unsecured websites or any websites that look suspicious and never give out your credit card or debit card information to someone over the phone unless you called them an know they are a legit business.