Why Do VPNs Get Blocked
Websites block VPN for many reasons; mainly copyright or censorship. In regions with strong digital surveillance, VPN blocking can be hard to get around. Here are some of the ways VPNs are blocked and what, if anything, you can do to get around it.
IP Blocks
Your VPN masks your real IP address and displays the server’s IP address instead. This means that when you open up Netflix US while connected to a US server, Netflix will see a US IP address. This should get you around any geo-restrictions, but not always.
Some sites keep a database of identified VPN IP addresses. If the server you log onto has an IP address in their database, that site blocks you immediately. Sites with tough geoblocks, like Netflix and BBC iPlayer, are very hard to access with a VPN.
Port Blocking
When VPNs connect to the internet, they usually use specific numbered ports. For example, OpenVPN security protocol usually sends traffic to port 1194.
This makes it easy to block certain types of traffic; the website just has to monitor that port and block any traffic it doesn’t want, VPN or other. Port blocking is less common than IP blocking, but you can get around it by switching ports.
Deep Packet Inspection (DPI)
DPI is the most difficult VPN blocking technique to circumvent. Instead of checking which ISP or port the traffic comes from, websites block traffic by the type of encryption they use.
VPNs do make your traffic anonymous, but certain security protocols, like OpenVPN, use unique cryptography signatures that a DPI can recognize and block. Most VPNs use OpenVPN as their default protocol, so sites simply recognize that encryption signature and block it. The traffic remains encrypted but it doesn’t get through.
This kind of VPN block is what the Great Firewall of China uses to restrict VPN use, which is one of the reasons why finding a VPN in China is so difficult. The only way to get around that is to change security protocols if your VPN allows it.
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