Common Censorship Techniques
💡 The Core Idea
Censors use a layered approach to blocking content, ranging from crude IP blocking to sophisticated deep packet inspection.
🧠The Toolkit
1. Packet Dropping (IP Blocking)
- Action: Drop all traffic to a specific IP address.
- Cons: High collateral damage (Overblocking). Shared hosting sites often put innocent sites on the same IP as blocked sites.
2. DNS Poisoning
- Action: Hijack the DNS resolution process to return a wrong IP.
- Pros: No overblocking (targets specific domain names).
3. TCP Reset (RST) Injection
- Action: Monitor traffic for keywords. If found, send a forged TCP RST packet to both client and server to kill the connection immediately.
4. Content Inspection (Proxies)
- Action: Route traffic through a proxy that reads the full content.
- Cons: Extremely expensive and hard to scale.