May 19, 2012, 7:23 AM — "When your data passes through a public network--such as the Wi-Fi at the coffee shop or airport--it is at risk." I've been writing variations on that sentence for 10 years now, and I expect I'll be writing it for many more. That's because it's easy to snoop on such networks, and the data on them isn't safeguarded against those prying eyes. You have to take action to keep your data safe. Fortunately, doing so doesn't have to be hard.
You could encrypt networked data one service at a time, by securing your email sessions or configuring your Twitter and Facebook accounts to use HTTPS. (Actually, I recommend both steps regardless of whatever other security measures you take.) But that means adjusting settings in lots of different apps, one at a time. There's a more comprehensive solution: a virtual private network (VPN).
When you set up a VPN on your Mac or iOS device, client software encrypts all of your outbound data (wrapping it in something often called a secure tunnel) and sends it to a secure server. That server has the appropriate encryption keys and other credentials to unwrap the data and send it along to wherever it's supposed to go. Likewise, the server returns data--requested webpages, email messages, or even streaming audio and video--to the client through the same tunnel; only the client can unravel those responses or streams.
VPNs are valuable because several segments of the path between you and the Internet are easy to exploit. It could be the segment from your Mac, iPhone, or iPad to the coffeeshop's Wi-Fi network. It could be the ethernet network behind the counter to which that router connects. In some cases, such as countries without a firm grasp on the idea of free speech, the weak link could even be the ISP that connects that coffeeshop to the Internet at large. VPNs can help protect your data along all of those vulnerable segments. (That's why VPNs have become critical tools for dissidents worldwide.)
Corporations use VPNs all the time, to keep communications to and from remote workers as secure as those that take place inside the office. Companies often require mobile workers and telecommuters to use the corporate VPN to connect to internal, for-employees-only servers. Using such secure links, those remote workers can also take advantage of the company's Internet connection--including filtering, virus-checking and firewall--for general Net access.