Web shield blocks many sites across multiple browsers

[jps-spld]

I had Avast One (free) installed for the greater part of a year and it worked fine.  Several days ago, it began blocking nearly all web sites whether I was using Firefox or Chrome.  I tried repairing it from the Add/Remove Program function in Windows, and that didn't improve it.  I just uninstalled it and installed Avast Free Antivirus instead.  More sites are now working, but I'm finding multiple sites I regularly visit are still blocked when using either browser.  I'm using Windows 10.

[DavidR]

The Web Shield works across multiple browsers.

Unfortunately without details it is almost impossible to comment.  Attach a couple of screenshots of the Avast Alert Window with the Details option selected, will help. See attached image on how to do this.  When posting use the Preview option if you don't see this.

Are you actually trying to connect to the sites that Avast is alerting on ?
If not try clearing the browser/s cookies, browsing cache and restart the browser.

[jps-spld]

There is no Avast alert window; Avast is not alerting on the sites. The browsers simply don't connect to the sites unless web shield is disabled.  Sorry I didn't describe this better in the OP.

Nevertheless, I just cleared cache and cookies in both Firefox and Chrome, and I'm still unable to connect to most sites. In fact, some sites I was temporarily able to connect to last night are again inaccessible.

[DavidR]

Can you give an example of some of the sites, just domain name only, not the https prefix, etc. as that would make the link active.

You can also try this site that checks sites are up or down.
https://downforeveryoneorjustme.com/

Was a Avast enabled when you were temporarily able to connect to some sites ?

[jps-spld]

For example, google.com, twitter.com, ebay.com, and basically anything else you can think of.  These sites were all up at the times I tried to access them, verified using other devices that I have and also by turning off Avast web shield temporarily. 

Avast.com seems to work fine with web shield on.

[DavidR]

My default browser on this win10 system is Firefox.
I use Google frequently and have just checked the three that you gave all opened without issue, including logging in to my ebay.

I don't use Avast One (I use Avast Antivirus free), so I'm not that familiar with it.  But it does seem strange that you are getting lots of no connections errors (rather than alerts).
Avast One does have other components not in the Avast Antivirus free, one that comes to mind is the VPN.

Other than not getting an avast alert are you getting any browser specific error messages and if so what ?

I don't know if this might have been better in the Avast One specific sub-forum - https://forum.avast.com/index.php?board=126.0 - or if there is a related post there.

[jps-spld]

Thanks for trying!

In Firefox I get this: "Secure Connection Failed An error occurred during a connection to www.xxxxxxxx.com. PR_END_OF_FILE_ERROR Error code: PR_END_OF_FILE_ERROR  The page you are trying to view cannot be shown because the authenticity of the received data could not be verified. Please contact the website owners to inform them of this problem."

Before coming here I did a bunch of troubleshooting around this error.  None of it worked. Then I checked the same sites in Chrome and realized that it wasn't a problem specific to the Firefox brower.

In Chrome I get:  "This site can’t be reached

www.xxxxxxx.com unexpectedly closed the connection.  Try:

Checking the connection
Checking the proxy and the firewall
Running Windows Network Diagnostics
ERR_CONNECTION_CLOSED"

I'm using Avast Free Antivirus now, although I started out Avast One.  Avast web shield seems to be the common denominator.  I'm not using any sort of VPN.

[DavidR]

The Web Shield, because of the way it works it has a security certificate

See this - https://blog.avast.com/2015/05/25/explaining-avasts-https-scanning-feature/ - article:

How Avast’s HTTPS scanning feature works (the short version)

Avast is able to detect and decrypt TLS/SSL protected traffic in our Web-content filtering component. To detect malware and threats on HTTPS sites, Avast must remove the SSL certificate and add its self-generated certificate. Our certificates are digitally signed by Avast’s trusted root authority and added into the root certificate store in Windows and in major browsers to protect against threats coming over HTTPS; traffic that otherwise could not be detected.

Avast whitelists websites if we learn that they don't accept our certificate. Users can also whitelist sites manually, so that the HTTPS scanning does not slow access to the site.

This last bit really shouldn't be that frequent, I have never had to use this in all of the time I have used Avast/Web Shield.  So I really do feel there is something else going on, what this is beyond my general knowledge of web site security and Avast.

I too did a search on - https://www.google.co.uk/search?q=PR_END_OF_FILE_ERROR - https://kinsta.com/knowledgebase/pr-end-of-file-error/
Avast whitelists websites if we learn that they don't accept our certificate. Users can also whitelist sites manually, so that the HTTPS scanning does not slow access to the site.

So depending on how a site is set up it may or may not recognise/accept this security certificate.  But given you are getting lots of blocks on sites that I'm having no issue with I think there is something else in the mix.

[Leo3487]

As only you have that problem and also given what said DavidRabout somethin else in the mix (or in the mid)

Also trying to figure, at Avast support say Avast whitelists websites if we learn that they don't accept our certificate.... DNS also could reject Avast certificate?

I wwould ttry to use manual DNS (8.8.8.8 and 8.8.4.4) instead ISP's DNS to discard a possible cause

[jps-spld]

Problem was apparently solved by uninstalling some remaining components of an old Bitdefender installation with the help of Bitdefender support.  I'm no sure why the problem arose after these programs coexisted peacefully for a really long time. But at least right now, Avast web shield is not preventing connection to legit websites.

[DavidR]

Thanks for the feedback.

Whilst it isn't advisable to have two active AVs installed as by their nature they are trying to get in first to prevent malware intrusion.  A bit like two dogs fighting over one bone.  Program updates,  can change how the AVs go about tasks in a different way which might bring them into conflict.

There can on occasion be remnants even after uninstalling an AV, for the most part it doesn't cause issues, but on occasion there may be remnants.  Most AVs also have a tool over and above the AVs Windows Uninstall function.

EDIT typo.

[jps-spld]

In this case, I used Bitdefender's tool and it didn't fully uninstall everything. Bitdefender's support was helpful and it eventually got done.