Monitoring Internet Censorship PDF
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Monitoring Internet Censorship part 2 Linux Day 2013 Napoli, October 26 2013 Giuseppe Aceto, [email protected] Premise – quick check We are going to see some “mechanics” of the Internet to explain how censorship works The description will avoid technicisms when possible No deep knowledge of computer networks will be implied but possibly a little introduction to “the Internet” basics SO – How many of you knows what the DNS is? – … and IP? – … and HTTP? – … IDS? 2 Monitoring Internet Censorship- Linux Day Napoli Oct.2013 Premise – quick check We are going to see some “mechanics” of the Internet to explain how censorship works The description will avoid technicisms when possible No deep knowledge of computer networks will be implied but possibly a little introduction to “the Internet” basics SO – How many of you knows what the DNS is? – … and IP? – … and HTTP? – … IDS? 3 Monitoring Internet Censorship- Linux Day Napoli Oct.2013 Basics about Internet: packets Information is divided in packets Packets are forwarded along a path SENDER-to-RECEIVER by several (usually<30) intermediate devices “routers” Packets are “labeled” with SENDER and RECEIVER addresses (sort of phone numbers, called “IP addresses”) – plus other details useful for the service Mumbo Mumbo Mumbo jumbo jumbo jumbo 4 Monitoring Internet Censorship- Linux Day Napoli Oct.2013 Basics about Internet: protocols The rules to write, split, label, forward, reassemble, read the messages are called protocols – Each one has its own business, some work together: often are wrapped in layers IP TCP HTTP Content HyperText Trasfer Protocol is concerned with providing web pages, identified by an Uniform Resource Locator (URL): http://www.foo.org/abc/bar.html protocol hostname path 5 Monitoring Internet Censorship- Linux Day Napoli Oct.2013 Basics about Internet: a lot happens TCP DNS (connection setup) (2) “foo.org” (3) “1.2.3.4” (1) Enter URL http://foo.org/bar.html (4) HTTP GET bar.html (5) Locate the (6) HTTP Response resource (7) Parse HTML & display (8) HTTP GET image1 (N) HTTP GET imageX Potentially many requests & responses Browser Web Server 6 Monitoring Internet Censorship- Linux Day Napoli Oct.2013 Access to content: an obstacle course http://thenextweb.com/asia/2010/01/05/route-gfw-flow-chart/ 7 Monitoring Internet Censorship- Linux Day Napoli Oct.2013 IP blocking 8 Monitoring Internet Censorship- Linux Day Napoli Oct.2013 9 Conventional Internet Censorship (1/2) Censor Firewall Censored net Uncensored net Alice Block Traffic Bob 9 Monitoring Internet Censorship- Linux Day Napoli Oct.2013 10 Conventional Internet Censorship (2/2) Censor Firewall Censored net Uncensored net Alice Block Traffic Bob For the censor: easy, cheap, but OVERBLOCKING issues 10 Monitoring Internet Censorship- Linux Day Napoli Oct.2013
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