Hotspot Shield depends on a custom VPN protocol that's not been publicly analyzed by independent experts. We don't know how private or secure it really is. The company has been accused of spying on users (it denies the allegations), and complaints abound online about Hotspot Shield software installing on PCs without users' permission. All this, and the company's U.S. location, may scare away customers who want to protect their privacy.
DNS servers are a bit like the phone books of the Internet: You can type in “thewirecutter.com,” for instance, and one of the many DNS servers behind the scenes can point you to the IP address of a server hosting the site. Most of the time, your DNS requests automatically route through your ISP, giving the ISP an easy way to monitor your traffic. Some VPN services rely on third-party DNS servers, but the best ones keep DNS servers in-house to prevent your browsing history, or your IP address, from getting out.
What's even scarier is the news that Hola, in certain instances, sells its users' bandwidth through a sister company. What that means, the safety experts say, is that if you're using Hola, your computer—working as an endpoint connection for other Hola users—could even be sold to shady characters for questionable or even illegal purposes as they try to stay anonymous on the Internet.
Mobile Apps: If you’re going to spend money on a VPN service provider (or even if you use a free one, frankly), you should be able to get a consistent experience across all of your devices. Most prominent providers offer desktop and mobile solutions for individual users, and while corporate and school networks may be a bit behind the curve here, they’re catching up too. Make sure you don’t have to use two different VPNs with two different policies and agreements just because you want to secure your phone along with your laptop.
When using the OpenVPN protocol, many VPN apps will give you the option of using either the TCP or UDP protocol. TCP is the protocol that you normally use to browse the web and download files. UDP is more common for streaming applications such as video, music, and gaming. The difference is in how computers and servers send network packets, the unit of data used to exchange information over the internet.
While you're connected to a VPN, all your network traffic passes through this protected tunnel, and no one—not even your ISP—can see your traffic until it exits the tunnel from the VPN server and enters the public internet. If you make sure to only connect to websites secured with HTTPS, your data will continue to be encrypted even after it leaves the VPN.