Censorship Detection Techniques
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Censorship detection techniques. Most of the credit goes to Jacob Appelbaum and this presentation was prepared last minute for the ESC2011 Italian hacker camp.
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Censorship Detection Techniques
- 1. Censorship detection Arturo `hellais` Filasto’ Sunday, September 4, 2011
- 2. Whoami • @hellais on twitter • hellais@torproject.org • art@globaleaks.org • art@fuffa.org • art@winstonsmith.org Sunday, September 4, 2011
- 3. What is Censorship? • Internet filtering is a form of non democratic oppression on people. • It allows those in power to subvert the reality. Sunday, September 4, 2011
- 4. Filternet • It’s a distorsion of what is in reality the internet. • Follows the subjectiveness of the authorities • This does not help humanity Sunday, September 4, 2011
- 5. La soluzione a quelli che sono percepiti soggettivamente come contenuti inappropriati è oggettivamente più contenuti Sunday, September 4, 2011
- 6. Tor • Tor software downloads are currently blocked from China, Iran, Lebanon, Qatar, etc. • Tor delivers via email, write to gettor@torproject.org and we will send you a client to bootstrap a Tor client Sunday, September 4, 2011
- 7. Hidden Services • They allow a server to give access to content anonymously • This bypasses censorship in place Sunday, September 4, 2011
- 8. Tor Hidden Services • am4wuhz3zifexz5u.onion • Anonymity for the Server • DoS protection • End-To-End encryption Sunday, September 4, 2011
- 9. How HS work Client Hidden Server IP IP IP Sunday, September 4, 2011
- 10. How HS work Client Hidden Server IP IP IP RP Sunday, September 4, 2011
- 11. Why use HS • Avoid retaliation for what you publish • Securely host and serve content • Stealth Hidden Service Sunday, September 4, 2011
- 12. How filtering is performed • Depends on the location and entities performing it • A mix of commercial products and open source software • Lebanon ISP’s use Free Software • Syria uses commercial Blue Coat devices • US/NSA use commercial Narus devices Sunday, September 4, 2011
- 13. Filtering taxonomy • Logging (passive) • Network and protocol Hijacking • Injection (modify content, 302, rst etc.) • Dropping (packets not transmitted) Sunday, September 4, 2011
- 14. Filter detection techniques • Important to classify by risk profile • People running filter detection tools must know how invasive the technique is Sunday, September 4, 2011
- 15. OONI • Open Observatory of Network Interference • I am working on this with Jacob Appelbaum as part of The Tor Project • An extensible and flexible tool to perform censorship detection Sunday, September 4, 2011
- 16. Existing testing tools • Netalyzr, rTurtle, Herdict. • Unfortunately either the raw data results or even the tools themselves are closed :( • They only release reports, without the original raw data Sunday, September 4, 2011
- 17. Goals for OONI • Make a something Open Source and publish the raw data collected • Have hackers write code and sociologist write reports ;) Sunday, September 4, 2011
- 18. Filtering detection techniques • High risk and Active • request for certain “bad” resources (test censorship lists) • keyword injection • anything that may trigger DPI devices • Low risk and Active • TTL walking • Network latency • Passive • In the future proxooni to proxy traffic with a SOCKS proxy and detect anomalies as the user does his normal internet activities Sunday, September 4, 2011
- 19. Fingerprinting of the application • Most existing tools that we audited leak who they are • In OONI reports will only be submitted over Tor Sunday, September 4, 2011
- 20. The scientific method • Control • What you know is a good result • It can also be a request done over Tor • Experiment • Check if it matches up with the result • If it does not there is an anomaly that must be explored Sunday, September 4, 2011
- 21. Brief excursus on censorship in the World Sunday, September 4, 2011
- 22. Syria: BlueCoat • They are using commerical bluecoat devices • Anonymous Telecomix contributors produced a good analysis Sunday, September 4, 2011
- 23. Syria: BlueCoat • SERVER is located outside Syria • CLIENT1 is located inside Syria • CLIENT connects to SERVER port 5060, no connection • CLIENT connects to SERVER port 443, connection works • CLIENT connects to SERVER port 80, the headers in the response are rewritten Sunday, September 4, 2011
- 24. Syria: BlueCoat GET /HTTP/1.1 Host: SERVER User-Agent: Standard-browser-User-Agent Accept: text/html,etc. Accept-Encoding: gzip,deflate,sdch Accept-Language: en-US,en;q=0.8 Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.3 X-Forwarded-For: CLIENT Cache-Control: max-stale=0 Connection: Keep-Alive X-BlueCoat-Via: 2C044BEC00210EB6 Sunday, September 4, 2011
- 25. Syria: BlueCoat • More details and funness to come in the following days ;) Sunday, September 4, 2011
- 26. Funny ⅖ Off Topic discovery • Who has ever used a captive portal? • Skype makes you pay access with it’s credit • It has problems doing login • It uses a captive portal Sunday, September 4, 2011
- 27. Sunday, September 4, 2011
- 28. Iran Sunday, September 4, 2011
- 29. Iran • Nokia has reportedly sold equipment to the Iranian government. It helps wiretap, track, and crush dissenting members of Iranian society. Nokia claims that this is ethical because they were forced to put legal intercepts into their products by the West. Sunday, September 4, 2011
- 30. Italy • Currently two methods are being used: • DNS based • ISP level blacklisting Sunday, September 4, 2011
- 31. Sunday, September 4, 2011
- 32. libero.it Sunday, September 4, 2011
- 33. Free communications • Are something that is important to the progress of humanity. Sunday, September 4, 2011
- 34. Questions? Sunday, September 4, 2011
- 35. Sunday, September 4, 2011