The field of information security has developed quickly in modern years because of the swift growth and widespread use of electronic data processing and also of business conducted through the Internet and other computer networks (LAN, WAN, etc.). The paper implemented here for the detection of Distributed Denial of Service (DDoS) attack using a pre-shared key exchange and entropy variation. This paper is implemented here for the detection of DDOS attack using the concept of filtering the packets using entropy variation and then generation of rules using decision tree provides efficient results as compared to the existing techniques implemented for the detection of DDoS attacks.