9,800 research outputs found
RAPTOR: Routing Attacks on Privacy in Tor
The Tor network is a widely used system for anonymous communication. However,
Tor is known to be vulnerable to attackers who can observe traffic at both ends
of the communication path. In this paper, we show that prior attacks are just
the tip of the iceberg. We present a suite of new attacks, called Raptor, that
can be launched by Autonomous Systems (ASes) to compromise user anonymity.
First, AS-level adversaries can exploit the asymmetric nature of Internet
routing to increase the chance of observing at least one direction of user
traffic at both ends of the communication. Second, AS-level adversaries can
exploit natural churn in Internet routing to lie on the BGP paths for more
users over time. Third, strategic adversaries can manipulate Internet routing
via BGP hijacks (to discover the users using specific Tor guard nodes) and
interceptions (to perform traffic analysis). We demonstrate the feasibility of
Raptor attacks by analyzing historical BGP data and Traceroute data as well as
performing real-world attacks on the live Tor network, while ensuring that we
do not harm real users. In addition, we outline the design of two monitoring
frameworks to counter these attacks: BGP monitoring to detect control-plane
attacks, and Traceroute monitoring to detect data-plane anomalies. Overall, our
work motivates the design of anonymity systems that are aware of the dynamics
of Internet routing
Conscript Your Friends into Larger Anonymity Sets with JavaScript
We present the design and prototype implementation of ConScript, a framework
for using JavaScript to allow casual Web users to participate in an anonymous
communication system. When a Web user visits a cooperative Web site, the site
serves a JavaScript application that instructs the browser to create and submit
"dummy" messages into the anonymity system. Users who want to send non-dummy
messages through the anonymity system use a browser plug-in to replace these
dummy messages with real messages. Creating such conscripted anonymity sets can
increase the anonymity set size available to users of remailer, e-voting, and
verifiable shuffle-style anonymity systems. We outline ConScript's
architecture, we address a number of potential attacks against ConScript, and
we discuss the ethical issues related to deploying such a system. Our
implementation results demonstrate the practicality of ConScript: a workstation
running our ConScript prototype JavaScript client generates a dummy message for
a mix-net in 81 milliseconds and it generates a dummy message for a
DoS-resistant DC-net in 156 milliseconds.Comment: An abbreviated version of this paper will appear at the WPES 2013
worksho
Hang With Your Buddies to Resist Intersection Attacks
Some anonymity schemes might in principle protect users from pervasive
network surveillance - but only if all messages are independent and unlinkable.
Users in practice often need pseudonymity - sending messages intentionally
linkable to each other but not to the sender - but pseudonymity in dynamic
networks exposes users to intersection attacks. We present Buddies, the first
systematic design for intersection attack resistance in practical anonymity
systems. Buddies groups users dynamically into buddy sets, controlling message
transmission to make buddies within a set behaviorally indistinguishable under
traffic analysis. To manage the inevitable tradeoffs between anonymity
guarantees and communication responsiveness, Buddies enables users to select
independent attack mitigation policies for each pseudonym. Using trace-based
simulations and a working prototype, we find that Buddies can guarantee
non-trivial anonymity set sizes in realistic chat/microblogging scenarios, for
both short-lived and long-lived pseudonyms.Comment: 15 pages, 8 figure
Content and popularity analysis of Tor hidden services
Tor hidden services allow running Internet services while protecting the
location of the servers. Their main purpose is to enable freedom of speech even
in situations in which powerful adversaries try to suppress it. However,
providing location privacy and client anonymity also makes Tor hidden services
an attractive platform for every kind of imaginable shady service. The ease
with which Tor hidden services can be set up has spurred a huge growth of
anonymously provided Internet services of both types. In this paper we analyse
the landscape of Tor hidden services. We have studied Tor hidden services after
collecting 39824 hidden service descriptors on 4th of Feb 2013 by exploiting
protocol and implementation flaws in Tor: we scanned them for open ports; in
the case of HTTP services, we analysed and classified their content. We also
estimated the popularity of hidden services by looking at the request rate for
hidden service descriptors by clients. We found that while the content of Tor
hidden services is rather varied, the most popular hidden services are related
to botnets.Comment: 6 pages, 3 figures, 2 table
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