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SUMMARY:Defending Networked Resources Against Floods of Unwelcome Requests
  - Michael Walfish - University of Texas\, Austin and University College L
 ondon
DTSTART:20081112T141500Z
DTEND:20081112T151500Z
UID:TALK13656@talks.cam.ac.uk
CONTACT:Mateja Jamnik
DESCRIPTION:The Internet is afflicted by unwelcome "requests"\, defined br
 oadly as claims on a scarce resource\, such as a server's CPU (in the case
  of spurious traffic whose purpose is to deny service) or a human's attent
 ion (in the case of spam). Traditional responses to these problems apply h
 euristics: they try to identify "bad" requests based on their content (e.g
 .\, in the way that spam filters analyze an email's text).\nThis talk argu
 es that heuristics are inherently gameable and that defenses should instea
 d aim to allocate resources proportionally to all clients (so if\, say\, 1
 0% of the requesters of some scarce resource are "bad"\, those clients sho
 uld be limited to 10% of the resources). \n\nTo meet this goal\, this talk
  presents two systems. The first is a denial-of-service mitigation in whic
 h clients are encouraged to automatically send *more* traffic to a besiege
 d server. The "good"\nclients can thereby compete equally with the "bad" o
 nes. The second is a distributed system for enforcing per-sender email quo
 tas to control spam. This system scales to a workload of millions of reque
 sts per second\, tolerates arbitrary faults in its constituent hosts\, and
  resists a variety of attacks. It achieves this fault-tolerance despite st
 oring only one copy (roughly) of any given datum and\, ultimately\, does a
  fairly large job with fairly little mechanism.\n
LOCATION:Lecture Theatre 1\, Computer Laboratory
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