  This paper presents a mitigation scheme to cope with the random query string
Denial of Service (DoS) attack, which is based on a vulnerability of current
Content Delivery Networks (CDNs). The attack exploits the fact that edge
servers composing a CDN, receiving an HTTP request for a resource with an
appended random query string never saw before, ask the origin server for a
(novel) copy of the resource. Such characteristics can be employed to take an
attack against the origin server by exploiting edge servers. Our strategy
adopts a simple gossip protocol executed by edge servers to detect the attack.
Based on such a detection, countermeasures can be taken to protect the origin
server and the CDN against the attack. We provide simulation results that show
the viability of our approach.

Cryptography and Security