Security KISS is a popular virtual private network tool used to protect privacy, ensure anonymity and bypass Internet restrictions. In this paper, we use Black-box analysis method and White-box analysis method to analyze the communication behavior and the encryption algorithm of the software. We get the workflow and the internal structures of the software in detail. In addition, we analyze the security of the software, and point out the defects existed. Finally, experimental results verify the accuracy and reliability of our analysis. This shows that the method we proposed to analyze network software is very efficient.