"Distributed Denial of Service (DDoS) attacks are a pressing problem on the Internet as demonstrated by recent attacks on major e-commerce servers and ISPs. Since their threat lies in the inherited weaknesses of the TCP/IP, an effective solution to DDoS attacks must be formulated in conjunction with a new networking paradigm, such as Active Networks. In this paper, we introduce a conceptual framework called Aegis, which we propose as a defense mechanism against DDoS attacks."