ZoneAlarm users face problems after installing new Windows patch

Half a dozen readers have written to me asking about a problem they experienced after downloading a routine Microsoft web update. Many users have suddenly found that they lost their ability to get online altogether.

The problem has finally been ferreted out: If you are running ZoneAlarm firewall software and install Microsoft patch KB951748, you're in trouble.

If you're reading this, you've probably already figured out that if you uninstall the Microsoft patch (in the Add or Remove Programs Control Panel, it's listed as "Security update for Windows (KB951748)") or roll back your system using System Restore, you won't have the problem. You can also uninstall ZoneAlarm to restore online functionality.

As of last night, there is a fix available for ZoneAlarm so you can keep both the Microsoft patch and your firewall up and running. Download it here by clicking on the link (under Recommended Actions) corresponding to the product you have, then you can reinstall the Microsoft patch.

Third-party security software products, especially firewalls, are always the first thing to cause havoc with Microsoft updates. In this case, the KB951748 patch was created to address an Internet-wide flaw in the way URLs are routed to websites; without the patch it is possible that even typing in a correct URL (like yahoo.com) could cause you to be redirected to a hostile website. But obviously Microsoft's fix had a conflict with ZoneAlarm's security system.

If you're running ZoneAlarm, do install the company's update and then, as all users should, install the Microsoft patch. It's an important security measure that could lead to serious problems down the road if you don't install it.

LINK: More details from BBC