Abstract: A method by one or more network devices implementing a scrubbing center for mitigating distributed denial of service attacks, where the scrubbing center is communicatively coupled to a plurality of clients and one or more servers. The method includes determining a set of packet fingerprints seen in a set of packets sent between the plurality of clients and the one or more servers, assigning a risk value to each packet fingerprint in the set of packet fingerprints based on analyzing previous security decisions made for packets having that packet fingerprint, and responsive to detecting an occurrence of a potential distributed denial of service attack, activating a security measure for each of one or more packet fingerprints in the set of packet fingerprints based on the risk value assigned to that packet fingerprint.