What technical means can be used to control access to websites and servers? We present three common methods of censorship. Plus, we show how to gain access to information.
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00:00Every time we connect to the Internet, data gets sent.
00:04Hang on, let's try this instead.
00:06Imagine a parcel with an address and sender info.
00:10Our parcels need to cross several, let's call them checkpoints.
00:14The Internet's postal service consists of routers or servers.
00:19In this system, there are many loopholes where governments can interfere.
00:25In terms of how governments restrict access to information on the Internet,
00:29I would say they can act at three different levels.
00:32This is Arturo Filasto from the Open Observatory of Network Interference.
00:37With colleagues, Arturo monitors Internet censorship
00:40and also knows the three most common strategies for Internet censorship used by governments.
00:47They can either interfere at the level of, let's say, the Internet's address book, DNS.
00:53Or they can choose to give you wrong directions in terms of accessing a particular site.
01:00The domain name system translates an IP address to a readable website name like dw.com.
01:10Authoritarian regimes often control DNS servers.
01:14This way, they can deregister domains.
01:17This blocks the translation from domain name to IP address and makes the website inaccessible.
01:25In some cases, they might just close the roads.
01:28They might say, when you're trying to go in a certain direction, your packets will not go through anymore.
01:34If you're going online, you probably have a contract with an Internet service provider.
01:39Governments controlling Internet service providers can blacklist website IPs.
01:44When you try to access a website, surveillance computers check whether the site has been blacklisted.
01:52And if it is on the blacklist, the ISP blocks the connection.
01:59In other cases, they might look at specific features or properties of your traffic.
02:04And they might decide that certain classes of traffic are allowed or disallowed.
02:09DPI is an advanced method of examining and managing network traffic.
02:15Governments use it to scan entire websites, including their protocols, for specific keywords.
02:22If flagged, the connection is blocked.
02:26You might receive an error message on your browser, even though in reality you're being censored.