Internet Censorship Flashcards
What is internet censorship?
Legal control or suppression of what can be accessed, published, or viewed on the Internet.
Name five ways internet censorship is implemented.
- IP address blocking
- DNS blocking
- Keyword filtering
- HTTP(S) filtering
- Protocol filtering
What is a censorship node?
Component of a system that can be used to evade internet censorship.
What does TCP/IP do?
Defines how data is sent and received over the Internet.
What is IP blocking?
Governments or ISPs (Internet Service Providers) can block access to specific IP addresses associated with censored websites, and have those requests rerouted or denied.
What can VPNs do?
Encapsulate traffic in encrypted tunnels, masking its true destination.
What can TOR do?
Anonymizes connections by routing them through multiple nodes.
What does HTTPS do?
Encrypts traffic, making it harder to inspect or block without also disrupting unrelated services.
What is Deep Packet Inspection?
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.
What is DNS tampering?
The DNS is manipulated to block or redirect access to certain websites.
What is decoy routing?
Redirects traffic to blocked content by embedding cryptographic signals in requests to seemingly benign destinations.
What is an End-to-Middle Proxy?
Proxies that sit between the user and the destination, routing traffic to bypass censorship.
What is Telex?
To circumvent censorship by embedding cryptographic signals in traffic that cooperating routers detect and reroute to blocked content.
What happens during HTTP filtering?
Censors inspect HTTP traffic and block or reset connections based on forbidden content or requests.
How does DNS blocking work?
Prevents domain names from being resolved to their IP addresses by manipulating DNS responses.
How is speed throttling used in censorship?
Bandwidth for certain protocols like HTTPS or SSH is limited, effectively slowing or disrupting access.
What censorship techniques were observed in Iran?
HTTP filtering, DNS filtering, and speed throttling with variations based on political events like elections.
How does the Great Firewall of China discover circumvention servers?
Using techniques like active probing, domain blocking, and keyword filtering.
What is collateral damage in censorship?
Blocking or disrupting access to unintended sites or services due to overly broad censorship techniques.
What are common tools to measure internet censorship?
On Hosts: RIPE Atlas, OONI Probe
Research Networks: PlanetLab
Remote Measurement: Augur, IRIS, Quack
What are challenges in measuring internet censorship?
Issues include establishing ground truth, achieving sufficient coverage, addressing ethical concerns, and ensuring continuity.
What are common methods to bypass censorship?
Encryption, VPNs, Tor, decoy routing, and end-to-middle proxies.
What is John Gilmour’s famous quote about censorship?
“The Internet treats censorship as a malfunction and routes around it.”
