Modular System for Mitigating Flood Attacks

Denial-of-Service (DoS) flooding attacks have become a serious threat to the reliability of the Internet. Web servers face all kinds of users; some of them engage malicious activities to degrade or completely block network services, such as flooding attacks. As a result, lots of resource and bandwidth on web sites might be wasted. While many approaches exist to filter network-level attacks, the application level attacks are harder to detect at the firewall. Filtering at this level can be computationally expensive and difficult to scale, while still producing false positives that block legitimate users. This paper presents a web application level approach to mitigate DoS attacks. The proposed method is to build a security gateway module with reverse proxy support that provides attack surface reduction enhancements against the HTTP Flood Attacks at the web application level. Web-based anomaly detection with reverse HTTP proxy which intercepts traffic and protects web application by providing users with a CAPTCHA to verify legitimate requests is used. Keywords— DoS, HTTP Flood Attack, CAPTCHA, False