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SUMMARY:Do You See What I See? Differential Treatment of Anonymous Users -
  Sheharbano Khattak\, University of Cambridge
DTSTART:20160216T140000Z
DTEND:20160216T150000Z
UID:TALK63162@talks.cam.ac.uk
CONTACT:Laurent Simon
DESCRIPTION:*Abstract:*\nThe utility of anonymous communication is undermi
 ned by a growing number of websites treating users of such services in a d
 egraded fashion. The second-class treatment of anonymous users ranges from
  outright rejection to limiting their access to a subset of the service’
 s functionality or imposing hurdles such as CAPTCHA-solving. To date\, the
  observation of such practices has relied upon anecdotal reports catalogue
 d by frustrated anonymity users. We present a study to methodically enumer
 ate and characterize\, in the context of Tor\, the treatment of anonymous 
 users as second-class Web citizens.\n\nWe focus on first-line blocking: at
  the transport layer\, through reset or dropped connections\; and at the a
 pplication layer\, through explicit blocks served from website home pages.
  Our study draws upon several data sources: comparisons of Internet-wide p
 ort scans from Tor exit nodes versus from control hosts\; scans of the hom
 e pages of top-1\,000 Alexa websites through every Tor exit\; and analysis
  of nearly a year of historic HTTP crawls from Tor network and control hos
 ts. We develop a methodology to distinguish censorship events from inciden
 tal failures such as those caused by packet loss or network outages\, and 
 incorporate consideration of the endemic churn in web-accessible services 
 over both time and geographic diversity. We find clear evidence of Tor blo
 cking on the Web\, including 3.5% of the top-1\,000 Alexa sites. Some bloc
 ks specifically target Tor\, while others result from fate-sharing when ab
 use-based automated blockers trigger due to misbehaving Web sessions shari
 ng the same exit node.\n\n*Bio:*\nSheharbano Khattak is a PhD student and 
 Research Assistant in the Security and NetOS groups of the Computer Lab\, 
 University of Cambridge\, under the supervision of Dr. Steven J. Murdoch\,
  Prof. Jon Crowcroft and Prof. Ross Anderson. She is externally advised by
  Prof. Vern Paxson at UC Berkeley. Sheharbano is a member of Robinson Coll
 ege and an Honorary Cambridge Trust Scholar. She likes to work on network 
 measurement and security in isolation\, and various combinations of these.
  Currently she studies the effects of online censorship from a number of d
 ifferent aspects: how it’s done\, how it can be stopped\, what its effec
 ts are\, and the evolving shape of the ecosystem of government/policy-base
 d censorship in particular. Previously she worked on Intrusion Detection S
 ystems and Internet malware with a focus on botnets.
LOCATION:LT2\, Computer Laboratory\, William Gates Building
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