Even with a VPN, open Wi-Fi exposes users

[Commentary] By now, any sentient IT person knows the perils of open Wi-Fi. Those free connections in cafes and hotels don't encrypt network traffic, so others on the network can read your traffic and possibly hijack your sessions. But one of the main solutions to this problem has a hole in it that isn't widely appreciated. Large sites like Twitter and Google have adopted SSL broadly in order to protect users on such networks. But for broader protection, many people use a virtual private network (VPN). Most people, if they use a VPN at all, use a corporate one. But there are public services as well, such as F-Secure's Freedome and Privax's HideMyAss. Your device connects with the VPN service's servers and establishes an encrypted tunnel for all your Internet traffic from the device to their servers. The service then proxies all your traffic to and from its destination. But there is a hole in this protection, and it happens at connect time.

The VPN cannot connect until you connect to the Internet, but the VPN connection is not instantaneous. In many, perhaps most public Wi-Fi sites, your Wi-Fi hardware may connect automatically to the network, but you must open a browser to a "captive portal," which comes from the local router, and attempt to gain access to the Internet beyond. You may have to manually accept a TOS (Terms of Service) agreement first. In this period before your VPN takes over, what might be exposed depends on what software you run. Do you use a POP3 or IMAP e-mail client? If they check automatically, that traffic is out in the clear for all to see, including potentially the login credentials. Other programs, like instant messaging client, may try to log on.

[Larry Seltzer is the former editorial director of BYTE, Dark Reading, and Network Computing at UBM Tech and has spent over a decade consulting and writing on technology subjects]