What is “Secure Core servers”? As opposed to what type of servers?
As per the website:
Free
Paid
Otherwise, yes. It just uses a more restricted number of servers available, and cap your net speed.
How much of a concern is this? Do other VPNs have similar defenses against this network monitoring?
If an attacker can get control of the VPN server, or monitor the network of the server, they will be able to match VPN clients with their traffic, nullifying the privacy benefits of the VPN.
Such timing/correlation attacks are not difficult to accomplish. In countries with restrictive Internet regulations (China, Russia, Iran, Turkey, etc), or countries with broad surveillance powers (USA, UK, etc), state surveillance agencies typically have the legal ability to coerce either the VPN provider, or the network/server provider of the VPN provider, to assist with such network monitoring. Therefore, even though Proton VPN is based in Switzerland, we cannot be certain that authorities are not monitoring our VPN servers located in those high-risk countries.
The biggest difference isn’t the secure core feature. Although this may help in some ways. What actually is way more important is the ability to filter dns requests. The paid version allows to block ads, malware and trackers this way. Also they have announced to add more customization to this the coming year.
Don’t expect a cow to fly, a VPN is not the right tool if you need to hide from your government.
As the previous poster mentioned, they are ok for privacy if all you are hiding from is surveillance capitalism or your IPS.