Michael Walfish Mythili Vutukuru Hari Balakrishnan David R. Karger Scott Shenker DDoS defense by offense. 303-314 2006 conf/sigcomm/2006 SIGCOMM http://doi.acm.org/10.1145/1159913.1159948 db/conf/sigcomm/sigcomm2006.html#WalfishVBKS06