The free version allows you to connect only one device, and you can use only one server in America – which will not work with Netflix, Hulu, or other popular streaming sites. You can still use it to access YouTube, Facebook, and other favorite social media sites that may be blocked. Plus, it’s compatible with all major operating systems, and it’s one of the fastest VPNs out there.
If you're of the iPhone persuasion, there are a few other caveats to consider for a mobile VPN. Some iPhone VPN apps don't use OpenVPN, even if the VPN service that made the app supports the protocol. That's because Apple requires additional vetting if a company wants to include OpenVPN with its app. VPN app developers have slowly started jumping through those extra hoops and are bringing support for protocols such as OpenVPN to iOS.
CHAP is an improvement over PAP because the clear-text password is not sent over the link. Instead, the password is used to create a hash from the original challenge. The server knows the client’s clear-text password and can, therefore, replicate the operation and compare the result to the password sent in the client’s response. CHAP protects against replay attacks by using an arbitrary challenge string for each authentication attempt. CHAP protects against remote-client impersonation by unpredictably sending repeated challenges to the remote client throughout the duration of the connection.
A mix of features and price make a good VPN, but plenty of bad VPNs masquerade as good ones. Look for articles written by trustworthy sources that discuss the merits of each service based on its features, versus simple rundowns and user testimonials, which are almost always polluted by a combination of fanatical users and corporate bootstrapping in attempt to get their names out to potential customers.
Additionally, moves from the FCC to remove rules regarding net neutrality have raised questions about VPNs. Without net neutrality rules, it's possible that ISPs could charge companies extra for access to "fast lanes" that would deliver content faster. ISPs could also create cable TV-style packages where you pay for individual access to websites. A VPN might be able to restore net neutrality, somewhat, by tunneling past ISP restrictions. Unfortunately, we'll have to see how all this plays out before we can say for certain how much a VPN might help.
VPN services, while tremendously helpful, are not foolproof. There's no magic bullet (or magic armor) when it comes to security. A determined adversary can almost always breach your defenses in one way or another. Using a VPN can't help if you unwisely download ransomware on a visit to the Dark Web, or if you foolishly give up your data to a phishing attack.