Several vendors opt for Cloud based website hosting nowadays, as it is very trustworthy, easily scalable and reasonable hosting solution than traditional website hosting in various aspects. The most common attacks carried out currently against web application are SQL injection. Cross Site Scripting (XSS), Distributed Denial of Service (DDoS) and Cross Site Request Forgery (CSRF). Distributed Denial-of-service (DDoS) attack is one of the major web security attacks to the cloud hosted websites. Hence, this paper mainly concentrates upon soft computing techniques used so far against such attack. The most straightforward way to carry out the attack is through botnet. The malicious HTTP traffic generated by an attacker imitates to be genuine and hence go undetected. Nowadays, different soft computing techniques are used as a tool to detect malicious traffic. This paper presents a review of these techniques implemented so far that differentiate between genuine and malicious traffic. Economic Denial of Sustainability (EDoS) is a special sort o f DDoS attack that exploits cloud's pay-as-you-go model. The attacker generates anomalous HTTP requests that cause up scaling of the architecture and this puts financial burden over website owner. This paper tries to realize whether existing techniques can be used for defending EDoS attack and it also points out research directions in this field. © 2017 IEEE.