Web browser keeps opening to msn by itself randomly

In the case of wifi, this can be fixed by simply disconnecting from the wireless network that has the captive portal. I'd also recommend unchecking the automatically connect option for any wifi network that has a captive portal, otherwise you'll be plagued by this.

Changing the registry setting is more of a nuclear option, so I recommend against using it unless you don't know what interface windows thinks has a captive portal. What you can try is disabling each network interface one at a time (including software interfaces, like tunnel or VPN interfaces.) Open the change network adapter settings applet (right-click the network icon in your systray, click view network connections, click change adapter settings) then try disabling those one at a time by right-clicking on the adapter icon and clicking disable.

Both a colleague and me had this with our Win10 company notebooks occurring with connections to an internal WiFi that requires authentication through a web page.

We both disabled EnableActiveProbing via registry key and it was instantly gone.

Probably happens when there's short connection drops but the session remains active so that instead of the redirect to a login page we hit MSN which is just intended as a 'probe'...

I'm sure, Microsoft had good intentions doing this but in environments with wireless networks sporting landing pages, but this is definitely going to confuse users more than it helps. I would say it isn't a good feature if even support professionals don't spot it and suggest clean Windows installs - which indeed wouldn't help because it IS a system feature.

Is there a statement from MS on this "defined behavior"?

this is for windows 10 not 8, browser opening to MSN randomly. but you can still have a look at the possible solution at the end of this thread may help may not with windows 8.

The Microsoft MVP has no idea whatsoever of why this is happening. Unfortunately, tech support people don't always know how to troubleshoot, and they rely on canned responses instead.

Windows does a periodic test for a captive portal. It tries to hit the URL http://www.msftconnecttest.com/redirect, and if that immediately results in a 301 or 302 HTTP response or if it is simply unreachable, then it assumes that you need to interact with a captive portal in order for you to have internet access. What it does in response is open your default browser to that URL. In order to prove this, try manually pasting that URL into your web browser and see if it results in you going to the same MSN page that your web browser periodically enters.

A few things to try in order to fix the problem:

First, if you're connected to more than one network (wired, wireless, or even a tunnel adapter, vpn adapter, or other virtual network adapter) try temporarily disabling all of them except for the one that is your primary route to the internet, and see if the problem goes away. If it does, then Windows is trying to probe one of those secondary interfaces, which is tripping up this detection.

If that doesn't work, then make sure you don't have a proxy or a firewall that is either blocking access to that URL, or redirects it to another page (say for example, a web page indicating that your access was denied.)

If that still doesn't work, then try the nuclear option: Modify the registry to disable active network probing. Here's a way to do that with a command console running as admin:

reg add "HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\NlaSvc\Parameters\Internet" /v EnableActiveProbing /t REG_DWORD /d 0 /f

Reboot after making that change, and the problem should go away.