CSE 592 INTERNET CENSORSHIP (FALL 2015) LECTURE 07 PROF. PHILLIPA GILL – STONY BROOK UNIVERSITY

WHERE WE ARE Admin note: Update on grades (coming soon!) Last time: Challenges of measuring censorship Principles to keep in mind when designing censorship measurements Ethics/legality (finishing this today) Creative solutions to the challenges SpookyScan Questions?

TEST YOUR UNDERSTANDING 1.What types of information controls might we want to study? 2.What sort of data/applications would we want to study in each case? 3.What does the lack of ground truth mean for how we interpret censorship data? 4.What challenges arise because of the adversarial environment where we make censorship measurements? 5.How can we try to reduce these challenges on our work? 6.What data sources might we correlate with to validate censorship? 7.What is the dual-use that censorship measurements can exploit? 8.What is an important property of communication channels for censorship? 9.Can someone explain how SpookyScan works?

TODAY Encore/Ethics of measuring censorship (wrap up of last time) Traffic Differentiation & Net Neutrality Glasnost

ENCORE: LIGHTWEIGHT MEASUREMENT OF WEB CENSORSHIP WITH CROSS-ORIGIN REQUESTS Governments around the world realize Internet is a key communication tool … working to clamp down on it! How can we measure censorship? Main approaches: User-based testing: Give users software/tools to perform measurements E.g., ONI testing, ICLabONI testingICLab External measurements: Probe the censor from outside the country via carefully crafted packets/probes E.g., IPID side channels, probing the great firewall/great cannonIPID side channelsgreat firewallgreat cannon 5

ENCORE: LIGHTWEIGHT MEASUREMENT OF WEB CENSORSHIP WITH CROSS-ORIGIN REQUESTS Censorship measurement challenges: Gaining access to vantage points Managing user risk Obtaining high fidelity technical data Encore key idea: 6 Script to have browser query Web sites for testing

ENCORE: USING CROSS SITE JAVA SCRIPT TO MEASURE CENSORSHIP Basic idea: Recruit Web masters instead of vantage points Have the Web master include a javascript that causes the user’s browser to fetch sites to be tested Use timing information to infer whether resources are fetched directly Operates in an ‘opt-out’ model User may have already executed the javascript prior to opting out Argument Not requiring informed consent gives users plausible deniability Steps taken to mitigate risk Include common 3 rd party domains (they’re already loaded by many pages anyways) Include 3 rd parties that are already included on the main site One project option is to investigate these strategies! Example site hosting Encore:

ETHICAL CONSIDERATIONS Different measurement techniques have different levels of risk In-country measurements How risky is it to have people access censored sites? What is the threshold for risk? Risk-benefit trade off? How to make sure people are informed? Side channel measurements Causes unsuspecting clients to send RSTs to a server What is the risk? Not stateful communication … … but what about a censor that just looks at flow records? Mitigation idea: make sure you’re not on a user device Javascript-based measurements Is lack of consent enough deniability?

TRAFFIC DIFFERENTIATION The act of identifying and discriminating against certain types of Internet traffic Example: Comcast + BitTorrent

Comcast's interference affects all types of content, meaning that, for instance, an independent movie producer who wanted to distribute his work using BitTorrent and his Comcast connection could find that difficult or impossible — as would someone pirating music.

THE RESULT?

WHAT EXACTLY IS TRAFFIC DIFFERENTIATION? Traffic is identified and performance is degraded How can traffic be identified? IP address Port Host name Payload Flow level characteristics Large body of work on “traffic classification” to identify different types of traffic Many products: e.g., Sandvine How might performance be degraded? Lower priority queues Spoofing dupacks (tested but not deployed)

UNDERLYING ISSUE: NET NEUTRALITY They want to deliver vast amounts of information over the Internet. And again, the Internet is not something that you just dump something on. It's not a big truck. It's a series of tubes. And if you don't understand, those tubes can be filled and if they are filled, when you put your message in, it gets in line and it's going to be delayed by anyone that puts into that tube enormous amounts of material, enormous amounts of material.

NET NEUTRALITY The principle that ISPs and governments should treat data on the Internet equally No discrimination (performance or cost) based on User, content, site, application, etc. Debated since early 00’s Mainly in context of last-mile providers wanting to block certain sites/protocols Example: A local ISP approached a colleague for a collaboration on traffic classification… guess why? Vint Cerf (co-inventor of IP), Tim Berners-Lee (creator of Web) speak out in favor of Net Neutrality

HISTORY OF NET NEUTRALITY IN US 2008 FCC serves cease and desist to Comcast in relation to BitTorrent blocking June 2010 US court of appeals rules that FCC doesn’t have power to regulate ISP networks or management of its practices Dec FCC Open Internet Order: bans cable television and phone providers from preventing access to competing services (eg., Netflix) 2012 variety of complaints: vs. AT&T (for restricting Facetime), Comcast (for restricting Netflix) Jan court says FCC doesn’t have authority to enforce net neutrality because ISPs are not “common carriers” Common carrier is liable for goods it carries E.g., oil pipelines ISPs treated like common carriers but not liable for third party content (e.g., slander, copyright infringement)

HISTORY OF NET NEUTRALITY IN US (2) As of Jan. ‘14 FCC could not enforce net neutrality because ISPs were not common carriers Issue: should ISPs be reclassified as common carriers (under Title II of the Communications act of 1934) Feb – FCC votes to apply common carrier status to ISPs Mar – FCC published new net neutrality rules Now net neutrality applies also to mobile networks

ALTERNATE VIEWS ON NET NEUTRALITY FCC rules about ``no blocking, no throttling and no paid prioritization’’ sound good but don’t address the real problem Key issue: lack of competition If ISPs had to compete on price and service there would be incentives for them to provide good performance Without competition… … ISPs can leave congested interconnects until content providers yield and pay for private interconnects Two technical mechanisms: Traffic differentiation: identify + degrade Interconnect congestion: refuse to provide higher bandwidth …forces content providers into paid private peerings Currently outside of the scope of the current FCC rules!

HOW CAN TECHNOLOGY HELP? Increasing transparency of traffic differentiation Give users tools to detect traffic differentiation when it happens Glasnost (reading presentation) Traffic Differentiator (ACKs: Slides prepared by Arash Molavi Kakhki (NEU) & Adrian Li (SBU)) Measure interconnect congestion _internet_interdomain_congestion_aims/mapping_internet_inte rdomain_congestion_aims.pdf

Goals Reliably detect differentiation in cellular networks On any app traffic Without requiring root privileges or OS modifications with few assumptions about traffic characteristics or packet shaper implementations Our approach is the only known way to test differentiation from non-rooted mobile devices 19

Related Work 20 SwitzerlandGlasnostUs Applications TestedP2PP2P and videoAny application Features TestedPacket manipulationPerformanceBoth Desktop AppYesBrowser pluginYes Smartphone AppNo Yes Previous work explored this problem for limited protocols and in limited environments. Other closely related work NetDiff, NetPolice, NANO, Bonafide

Key Contributions Design and implementation of a traffic differentiation detecting system Validation of our approach using commercial shaping devices Evaluating statistical techniques for identifying such differentiation An Android app for any user to run our tests and see the results from our server 21

Record & Replay Record: 2- Replay:

Methodology 23 Record target application traffic using meddle and tcpdump Replay traffic alternately, tunneled and untunneled Parse pcap and create transcript of packets Analyze throughput, RTT, jitter, packet loss Record: Avoid running TCPDUMP on users’ devices. Utilize Meddle (a VPN proxy over IPsec) to record network traffic.

Methodology 24 Record target application traffic using meddle and tcpdump Replay traffic alternately, tunneled and untunneled Parse pcap and create transcript of packets Analyze throughput, RTT, jitter, packet loss Parse: Create two objects, one for the client side and one for server side. Handle unrelated/noise traffic. Parser client server

Methodology 25 Record target applicatio n traffic using meddle and tcpdump Replay traffic alternately, tunneled and untunneled Parse pcap and create transcript of packets Analyze throughput, RTT, jitter, packet loss Replay: replay the salient features of application traffic such that it will be subject to differentiation from middleboxes alternate tunneling and plaintext to control visibility for packet shapers

Methodology 26 Record target applicatio n traffic using meddle and tcpdump Replay traffic alternately, tunneled and untunneled Parse pcap and create transcript of packets Analyze throughput, RTT, jitter, packet loss Analyze: quantify differentiation in term of throughput, round trip time, jitter, loss, … Analyzer

Proof of Concept 27 Replay produces traffic nearly identical to the original traffic.

Validation: VPN Overhead 28 VPN overhead introduced by: IPsec encapsulation Latency added by going through the VPN server We put VPN and replay server on the same machine to minimize latenc y

Validation: Detectable? 29 Shaper effect on YouTube replay traffic

Validation: Shaping Result 30 Effect of changing different parameters of YouTube traffic on detection of commercial shaping device Changes in traffic Detection result using: Original portsDifferent ports No changesYouTube Added a packet with 1 byte of data to the beginning of trafficHTTPP2P Added 1 byte of random data to the beginning of first packetHTTPP2P Replaced “GET” with a random string (same size)HTTPP2P Replaced “youtube” string with a random one (first packet only)HTTPP2P Replaced “youtube” string with a random one (first packet, HOST header only) YouTube Added one byte of random data to the end of first packetYouTube Added “GET” to beginning of first packetYouTube

Evaluating Techniques 31 How to determine differentiation? Hard to detect shaping here!

Techniques Comparison 32 Comparison of two-sample KS test (NetPolice ) and our Weighted KS test We allow a difference up to: threshold t = a max /w a/w

Accuracy 33 Accuracy against loss Accuracy for different apps

HOW CAN TECHNOLOGY HELP? Increasing transparency of traffic differentiation Give users tools to detect traffic differentiation when it happens Glasnost (reading presentation) Traffic Differentiator (ACKs: Slides prepared by Arash Molavi Kakhki (NEU) & Adrian Li (SBU)) Measure interconnect congestion _internet_interdomain_congestion_aims/mapping_internet_inte rdomain_congestion_aims.pdf

HANDS ON ACTIVITY Try Differentiation detector app (Differentiation detector in Android market)