The exponential advancement in the internet technologies in 21th century has not only brought convenience and efficiency in the daily life but more importantly, guaranteed the interconnected global society via web service. Paradoxically, it is because of this form of advancement, cybersecurity is now a huge threat to everyone and causing massive financial and sometimes physical damages to various servers. Denial of Service (Dos) attacks have now become a common form of attack that is a massive threat to modern day internet. Especially, Distributed Denial of Service (DDoS) attack controls multiple sources and blast traffic simultaneously to the target therefore interrupting or suspending services of the host connected to the Internet.  This form of attacks are more hidden, which makes it more difficult to detect and defend against than a simple DoS attack form a single host. in the report, the general overview of DDoS attacks will be addressed and simulated on Wi-fi environment to observe the effect of DDoS on a client-server.