Avast blocks Internet access to public wi-fi

[KNRover]

I frequent a restaurant less than a mile from my house that has public wi-fi.  The first time I took my Toshiba laptop there, it said it was connected, but had "No Internet access".  I asked one of the waiters to reboot the router, which he did, but it made no difference.  Nobody was available who knew anything about the system.

The 2nd time I tried it, the owner was there.  I had the same problem, but two people at the bar had smart phones and both had Internet access.  The owner told me that as soon as you connect, you're supposed to see a "Terms & Conditions" statement (a mini EULA) that you have to agree to before you can have Internet access.  It did not appear on my Toshiba.  I immediately concluded that something on my computer was blocking the "EULA".  First thing I tried was to disable Avast's shields.  The instant I did, the EULA appeared, I clicked OK and had Internet access.

Why did Avast block my computer's access to the EULA?  Which shield is doing it, and how do I tell it not to block this and in fact all public wi-fi connections?

[DavidR]

You leave out a crucial piece of information, what version of avast are you using free/pro/ais build 7.0.1456.

Only the avast Internet Security version has a firewall, so if you don't have AIS then avast doesn't block, it only scans and alerts to infection. Presumably this isn't the case or you would have mentioned that ?

[KNRover]

Sorry.  I have the current free version (7.0.1456), not AIS.  It was blocking the appearance of the EULA which you must accept before gaining Internet access.  I only found out from the restaurant owner that a EULA was supposed to pop up when you connected; would otherwise not have known it existed.  After he told me that, I first disabled the Windows firewall.  Still no EULA.  I then turned the firewall back on and disabled the Avast shields.  Bingo!  EULA appeared immediately, I clicked OK and then had Internet access.

At no time did I see a warning from Avast that it detected a threat.

I could be wrong about the EULA not making itself visible.  I occasionally encounter programs that I open, but see nothing onscreen.  But when I check the Taskbar, there it is, minimized.  Why that happens, I don't know.  Might be the case with the EULA.  I'm going to test that possibility today will report back what I find.

[DavidR]

You say it was blocking, but as said avast doesn't block, it scans and alerts to infection, it isn't its intention to specifically block as it isn't a firewall.

So there has to be some sort of interaction going on to stop the eula pop-up (this interaction wouldn't happen with no shields), there is presumably some sort of script to pop-up that eula screen. I don't know what browser you were using (?) if that had pop-up blocking enabled or an add-on to block pop-ups and these might have some interaction. Whilst this interaction is going on, somehow the pop-up either fails or times out, so it doesn't get displayed.

By disabling all of the shields (aside from a risk, especially on a public wifi), you aren't narrowing it down to see where that interaction might lie. Because I believe there is some sort of script involvement to display the pop-up, the avast script shield may have an interaction (so I would have started with disabling the script shield). If that didn't work the next area would be Web Shield as that has a direct interaction in that your browser's http traffic is redirected through the web shield proxy. The web shield doesn't monitor any https (secure encrypted traffic/protocol), so switching between http and https pages would be an area to investigate.

Obviously no one can physically check this out for you to see A) the source code of the initial page, B) the URLs of the pages involved and C) how the eula pop-up is called (if there is any switching from http to https and possibly back to http connections). We would have to be in the restaurant trying to connect to the public wifi to be able to determine the above.

[lakrsrool]

Sorry.  I have the current free version (7.0.1456), not AIS.  It was blocking the appearance of the EULA which you must accept before gaining Internet access.  I only found out from the restaurant owner that a EULA was supposed to pop up when you connected; would otherwise not have known it existed.  After he told me that, I first disabled the Windows firewall.  Still no EULA.  I then turned the firewall back on and disabled the Avast shields.  Bingo!  EULA appeared immediately, I clicked OK and then had Internet access.

At no time did I see a warning from Avast that it detected a threat.

I could be wrong about the EULA not making itself visible.  I occasionally encounter programs that I open, but see nothing onscreen.  But when I check the Taskbar, there it is, minimized.  Why that happens, I don't know.  Might be the case with the EULA.  I'm going to test that possibility today will report back what I find.

It was probably minimized.... that happens sometimes for various reasons and can fool a person if they don't check the task bar.