We're not cryptography experts, so we can't verify all of the encryption claims providers make. Instead, we focus on the features provided. Bonus features like ad blocking, firewalls, and kill switches that disconnect you from the web if your VPN connection drops, go a long way toward keeping you safe. We also prefer providers that support OpenVPN, since it's a standard that's known for its speed and reliability. It's also, as the name implies, open source, meaning it benefits from many developers' eyes looking for potential problems.
Trust and transparency issues are the foremost concerns in choosing a great VPN, and if a service doesn’t have enough locations to be useful to you, all the security features won’t make a difference. But after those concerns have been satisfied, we recommend that most people use connections based on the OpenVPN protocol, because of security flaws and disadvantages in the PPTP and L2TP/IPsec protocols. (Experienced users may consider IKEv2, but because it has its own debated pros and cons, we ruled it out.) Though AES 128-bit encryption is fine for most purposes, we prefer services that default to the more-secure 256-bit encryption and still offer good performance.
HotSpot Shield is a product that has had some ups and downs in terms of our editorial coverage. Back in 2016, they picked up some very positive coverage based on founder David Gorodyansky comments about protecting user privacy. Then, in 2017, a privacy group accused the company of spying on user traffic, an accusation the company flatly denies. Finally, just this year, ZDNet uncovered a flaw in the company's software that exposed users. Fortunately, that was fixed immediately.