摘要：Botnet-based distributed denial of service (DDoS) attacks represent an emerging and sophisticated threat for today’s Internet. Attackers are now able to mimic the behavior of legitimate users to a great extent, making the issue of countering these attacks very challenging. This paper proposes a novel scheme to mitigate botnet-based DDoS attacks. The proposed scheme, called JUST-Google, utilizes Google’s strategic position as an entrance for today’s Internet to distinguish between legitimate traffic and attack traffic. The main idea of JUST-Google is to let ISP’s edge routers allow traffic originating from sources that are approved by Google and destined to a victim within that ISP to pass while filtering all other traffic destined to the same victim. In this context, we propose that GoogleTM can offer a paid service to identify legitimate sources by directing users who want to access a web site under attack to a group of nodes that will perform authentication in which users are required to solve a reverse Turing test to obtain access to the web server. We evaluate the proposed scheme through a combination of theoretical analysis and experimental studies. Our studies show that JUST-Google provides a great chance for legitimate clients to access a web site that is under a botnet-based DDoS attack without imposing a significant overhead.
