The AVISPA Tool is a push-button tool for the Automated Validation of Internet Security Protocols and Applications. It provides a modular and expressive formal language for specifying protocols and their security properties, and integrates different back-ends that implement a variety of automatic protocol analysis techniques. Experimental results, carried out on a large library of Internet security protocols, indicate that the AVISPA Tool is a state-of-the-art tool for Internet security protocol analysis as, to our knowledge, no other tool exhibits the same level of scope and robustness while enjoying the same performance and scalability.