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In my country, internet service providers offer YouTube only, work and learn packages, and Twitter only packages.
I activated YouTube only package and used a VPN. But I can only go to youtube and can't do internet surfing even though I am using a VPN. But as I know, a VPN encrypts the traffic, right? How do service providers block it?
I am using AVAST VPN. How is this technically possible?
As @schroeder suggests, if your ISP provides access only to Youtube and Twitter, it means that you can't connect to the VPN server and actually create a VPN. That's because your VPN server's domain differs from Youtube's or Twitter's domains so your ISP blocks any access to it. If that's true (you'll have to confirm yourself) that means that you don't use a VPN when you're surfing, so your ISP is able to block everything aside from Youtube and Twitter.
If your isp allowed vpn, then even though your traffic is encrypted they know the size of packages. Youtube videos will be large. That can be detected even with encryption. Twitter packages are small. That can also be detected. It’s not perfect.
If the isp installed software on your computer to enforce you only use youtube and Twitter, that software can send youtube and Twitter through vpn and block everything else.
