Now a days, Use of Internet is increased day by day. Both Technical and non technical people use the Internet very frequently but only technical user can understand the aspects working behind Internet. There are different types of protocols working behind various parameters of Internet such as security, accessibility, availability etc. Among all these parameters, Security is the most important for each and every internet user. There are many security protocols are developed in networking and also there are many tools for verifying these types of protocols. All these protocols should be analyzed through the verification tool. AVISPA is a protocol analysis tool for automated validation of Internet security protocol and applications. In this paper, we will discuss about Avispa library which describes the security properties, their classification, the attack found and the actual HLPSL specification of security protocols.