The attack surface of an RFID system is the set of points where an attacker can interact with or influence the system. Different types of RFID vulnerabilities may affect different parts of the system, such as the tags, the readers, the middleware, or the backend database. Therefore, the most important consideration in selecting a security testing method based on different RFID vulnerability types is to have an understanding of the attack surface and the potential threats and risks associated with each part of the system. This will help to choose the most appropriate and effective testing method, such as passive or active scanning, tag cloning or spoofing, replay or relay attacks, or cryptographic analysis. References: Official (ISC)2 CISSP CBK Reference, Fifth Edition, Domain 6: Security Assessment and Testing, pp. 1055-1056; CISSP All-in-One Exam Guide, Eighth Edition, Chapter 10: Security Assessment and Testing, pp. 1039-1040.