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