How Can an Internet Provider Block a VPN?

Method	Description	Effectiveness	Tools Used
IP Blocking	Blocking access to known IP addresses used by VPN servers.	High	IP Blacklists, Firewalls
Deep Packet Inspection (DPI)	Analyzing internet traffic to identify VPN signatures.	Very High	DPI Tools, Network Analyzers
Protocol Blocking	Blocking specific VPN protocols (e.g., OpenVPN, PPTP).	Medium	Firewalls, Protocol Filters
Throttling VPN Traffic	Reducing the bandwidth of VPN traffic to make the connection slow.	Moderate	Bandwidth Shaping Tools
Port Blocking	Blocking ports commonly used by VPN protocols (e.g., TCP 443, UDP 1194).	Medium	Firewall Rules
Forcing DNS Leaks	Manipulating DNS queries to bypass VPN protection.	Low	DNS Hijacking Tools

What is VPN Blocking?

VPN (Virtual Private Network) blocking refers to the practice of Internet Service Providers (ISP) or governments preventing users from using VPN services. VPNs are commonly used to bypass censorship, secure browsing activity, and access geo-blocked content, but ISPs may block them to enforce internet policies or comply with government regulations.

Here are the most common methods used by ISPs to block VPN services and how they work.

IP Address Blocking

One of the simplest ways for an ISP to block a VPN is by blocking known IP addresses associated with VPN servers. VPN providers have a range of IP addresses assigned to their servers, and ISPs can block these IPs, preventing users from connecting to VPNs.

• Tools used: ISPs use IP blacklists and firewalls to block access to these IPs.
• Effectiveness: This method is highly effective for mainstream VPN providers but can be circumvented by changing IPs or using VPNs with rotating IP addresses.

Deep Packet Inspection (DPI)

Another more advanced method is Deep Packet Inspection (DPI). With DPI, ISPs can inspect data packets and identify whether the traffic is VPN-based by analyzing the structure of the packets.

• Tools used: DPI tools and network analyzers scan traffic to distinguish between encrypted VPN traffic and regular HTTPS traffic.
• Effectiveness: DPI is very effective, especially in countries like China, where VPNs are heavily restricted. However, some VPNs have implemented obfuscation techniques to make their traffic appear like regular web traffic, bypassing DPI.

Blocking VPN Protocols

VPN protocols like OpenVPN, L2TP/IPsec, and PPTP are used to establish encrypted connections between users and VPN servers. ISPs can block these specific protocols by identifying their signatures in the traffic and preventing connections using these protocols.

• Tools used: Firewall rules are set up to block specific ports or traffic that matches the signature of VPN protocols.
• Effectiveness: This method is moderately effective. Some VPNs offer alternative protocols like WireGuard or Stealth VPN, which are designed to evade protocol blocking.

VPN Traffic Throttling

Rather than blocking VPNs outright, some ISPs opt to throttle VPN traffic by slowing down internet speeds when they detect a VPN is in use. This can make the VPN connection nearly unusable due to slow speeds.

• Tools used: ISPs use bandwidth shaping tools to reduce the speed of encrypted traffic typically associated with VPNs.
• Effectiveness: While not a complete block, throttling makes using VPNs less attractive. Many users switch to protocols or servers that are less likely to be throttled.

Port Blocking

Most VPN protocols rely on specific ports for communication. For example, OpenVPN commonly uses port 1194 (UDP), while other VPNs use port 443 (TCP). ISPs can block these ports to disrupt VPN traffic.

• Tools used: ISPs configure firewalls to block access to the commonly used ports for VPNs.
• Effectiveness: This method is moderately effective. Some VPNs allow users to switch to less common ports, making this tactic less reliable over time.

DNS Manipulation and Forcing DNS Leaks

Some ISPs use DNS hijacking techniques to force DNS leaks, where even if a user is connected to a VPN, their DNS queries bypass the VPN and are sent to the ISP’s DNS servers. This exposes the websites the user is visiting, even if their connection is encrypted.

• Tools used: DNS hijacking or DNS filters are applied to route traffic away from VPN servers.
• Effectiveness: This is a less effective method but can still compromise the privacy of VPN users. Many modern VPNs include features to protect against DNS leaks.

How Can You Bypass VPN Blocking?

There are several ways to get around VPN blocks imposed by your ISP or government:

1. Obfuscation Technology – Some VPN providers use obfuscation to make their traffic look like regular web traffic, making it harder for ISPs to detect and block.
2. Use Different Ports – Some VPN services allow you to switch to less common ports that are not as easily blocked by ISPs.
3. Switch VPN Providers – Choosing a VPN with a large range of IP addresses and rotating servers can help you avoid blocks based on IP blacklists.
4. Use a Shadowsocks Proxy – Shadowsocks is a proxy service that’s designed to bypass censorship and is harder to detect than traditional VPN protocols.

Conclusion

ISPs have a variety of tools at their disposal to block or restrict VPN use, from simple IP blocking to advanced DPI and protocol filtering. Understanding these methods can help you find ways to circumvent them and maintain your online privacy and access. Selecting a VPN that uses modern techniques like obfuscation and offering multiple protocol options will give you the best chance of bypassing ISP restrictions.

However, keep in mind that no method is foolproof, and some ISP blocks can be very hard to bypass, especially in countries with strong internet censorship laws like China.