Windows 8 / 8.1, and possibly 7, will auto-launch a web browser on connection to a wifi network with a captive portal. This is a security risk -- anyone could set up a wifi network with malicious script in the capture page, and windows would automatically navigate to it without user intervention. Or, on a public wifi network with such a portal (such as an airport), malicious code could be injected in transit by an intercepting access point. To turn this behaviour off: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\NlaSvc\Parameters\Internet set 'EnableActiveProbing' to 0 (the default value is 1) Then restart the computer. According to http://technet.microsoft.com/en-us/library/cc766017(WS.10).aspx "Setting the value to 0 prevents NCSI from connecting to a site on the Internet during checks for connectivity." See also http://blog.superuser.com/2011/05/16/windows-7-network-awareness/