What Is a Firewall? From Basic Concepts to National Internet Censorship
In today’s internet, firewalls are essential tools used for both cybersecurity and traffic censorship. While individuals and companies use firewalls to protect their systems, governments may deploy national-level firewalls to control information access.
This guide introduces what a firewall is, and how it’s used in broader systems of surveillance and restriction by ISPs and authorities.
🔒 What Is a Firewall?
A firewall is a system that controls the incoming and outgoing network traffic based on predefined security rules. It acts as a barrier between a trusted network (like your home or device) and untrusted networks (like the public internet).
Firewalls can be hardware devices or software tools and are used to:
- Block malicious traffic
- Filter content
- Restrict access to certain services
🧱 What Is a National Firewall?
A national firewall is a government-level system that monitors, filters, and controls internet traffic at scale. Usually deployed in cooperation with ISPs, it can:
- Block access to foreign websites and apps
- Intercept encrypted traffic
- Restrict messaging or social media
- Temporarily limit internet access during events (elections, protests, etc.)
🔍 Common Techniques Used in Network Censorship
1. DNS Spoofing / Tampering
Returns fake or invalid IP addresses for banned websites, making them appear offline.
2. IP Address Blocking
Blocks traffic to/from specific IP addresses or entire ranges, affecting other services on shared servers.
3. HTTP Keyword Filtering
Filters traffic based on keywords or URLs in plain-text HTTP requests (ineffective against HTTPS).
4. SNI Inspection & TLS Fingerprinting
Detects which domain is being accessed during the TLS handshake and identifies VPN/proxy clients.
5. Traffic Fingerprinting
Analyzes traffic patterns (packet size, timing, frequency) to identify proxy or tunneling tools.
6. Active Probing
The firewall actively connects to suspected proxy/VPN servers to detect their behavior and block them.
🛰️ ISP-Level Restrictions
Beyond national-level firewalls, some internet service providers (ISPs) also implement their own controls:
- Blocking VPN protocols or ports (e.g., OpenVPN, WireGuard)
- Throttling encrypted traffic or streaming services
- Filtering specific content categories (e.g., adult, gambling, torrent sites)
- Enforcing time-based restrictions on social media or chat platforms
✅ Summary
Modern firewall systems go beyond simple blacklists. They combine deep packet inspection, statistical analysis, and active interference to restrict internet access.
To maintain your privacy and access freedom, it’s essential to use a secure and well-configured VPN like VineVPN, which offers protocol obfuscation, encrypted DNS, and global high-speed servers.