Users of Avast antivirus software complain on the company’s forums that they are no longer able to visit websites and can’t update Windows. The issue appears to be caused by a buffy update of the antivirus software.
The root of the cause seems to be the Web Shield feature of the software, which scans the visited websites and blocks malicious code. Users report that as soon as they disable this feature that they have access to the internet again.
Most users report their issues started after they updated to version 17.4.2294. For some a reinstall of the software solved their problem.
The issue might affect a large number of users, Avast holds a market share of 21%, according to Opswat. Far more than ESET with 12.5% the second largest antivirus vendor.