Internet Censorship

Question 1

What is internet censorship?

Answer 1

Legal control or suppression of what can be accessed, published, or viewed on the Internet.

Question 2

Name five ways internet censorship is implemented.

Answer 2

1. IP address blocking
2. DNS blocking
3. Keyword filtering
4. HTTP(S) filtering
5. Protocol filtering

Question 3

What is a censorship node?

Answer 3

Component of a system that can be used to evade internet censorship.

Question 4

What does TCP/IP do?

Answer 4

Defines how data is sent and received over the Internet.

Question 5

What is IP blocking?

Answer 5

Governments or ISPs (Internet Service Providers) can block access to specific IP addresses associated with censored websites, and have those requests rerouted or denied.

Question 6

What can VPNs do?

Answer 6

Encapsulate traffic in encrypted tunnels, masking its true destination.

Question 7

What can TOR do?

Answer 7

Anonymizes connections by routing them through multiple nodes.

Question 8

What does HTTPS do?

Answer 8

Encrypts traffic, making it harder to inspect or block without also disrupting unrelated services.

Question 9

What is Deep Packet Inspection?

Answer 9

Analyze the content of TCP packets. If certain keywords, domains, or types of traffic (VPNs or Tor) are detected, the packets can be dropped or redirected, effectively blocking access.

Question 10

What is DNS tampering?

Answer 10

The DNS is manipulated to block or redirect access to certain websites.

Question 11

What is decoy routing?

Answer 11

Redirects traffic to blocked content by embedding cryptographic signals in requests to seemingly benign destinations.

Question 12

What is an End-to-Middle Proxy?

Answer 12

Proxies that sit between the user and the destination, routing traffic to bypass censorship.

Question 13

What is Telex?

Answer 13

To circumvent censorship by embedding cryptographic signals in traffic that cooperating routers detect and reroute to blocked content.

Question 14

What happens during HTTP filtering?

Answer 14

Censors inspect HTTP traffic and block or reset connections based on forbidden content or requests.

Question 15

How does DNS blocking work?

Answer 15

Prevents domain names from being resolved to their IP addresses by manipulating DNS responses.

Question 16

How is speed throttling used in censorship?

Answer 16

Bandwidth for certain protocols like HTTPS or SSH is limited, effectively slowing or disrupting access.

Question 17

What censorship techniques were observed in Iran?

Answer 17

HTTP filtering, DNS filtering, and speed throttling with variations based on political events like elections.

Question 18

How does the Great Firewall of China discover circumvention servers?

Answer 18

Using techniques like active probing, domain blocking, and keyword filtering.

Question 19

What is collateral damage in censorship?

Answer 19

Blocking or disrupting access to unintended sites or services due to overly broad censorship techniques.

Question 20

What are common tools to measure internet censorship?

Answer 20

On Hosts: RIPE Atlas, OONI Probe
Research Networks: PlanetLab
Remote Measurement: Augur, IRIS, Quack

Question 21

What are challenges in measuring internet censorship?

Answer 21

Issues include establishing ground truth, achieving sufficient coverage, addressing ethical concerns, and ensuring continuity.

Question 22

What are common methods to bypass censorship?

Answer 22

Encryption, VPNs, Tor, decoy routing, and end-to-middle proxies.

Question 23

What is John Gilmour’s famous quote about censorship?

Answer 23

“The Internet treats censorship as a malfunction and routes around it.”