How censorship works

DW (English)

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.

Transcript

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.

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