This document provides an overview of ATM malware threats. It describes the XFS subsystem that is commonly used in ATMs to interface with devices from different vendors. The XFS architecture and important APIs are explained. The evolution of ATM malware from skimmers to more advanced malware like RIPPER is documented. RIPPER is able to read magnetic stripe and EMV chip data as well as control the cash dispenser. The document concludes with a reference to analyze the RIPPER malware code.