Skimmer Scanner Android App is open source and available to download from Google Play Store for Android users. It listens all the serial traffic passed between credit card readers and save it to external disks. Check for obvious signs of tampering at the top of the ATM, near the speakers, the side of the screen, the card reader itself, and the keyboard. If something looks different, such as a different color or material, graphics that aren’t aligned correctly, or anything else that doesn’t look right, dont use that ATM.”]
Source: https://gbhackers.com/android-credit-card-skimmer-scanner/