Trusted Sites With IE ESC Turned On

Enterprise, Microsoft

When protecting users from malicious internet sites on servers, we can keep Internet Explorer Enhanced Security Configuration turned on (that’s the default). However, with the setting on, almost no modern website will properly load.

The solution is to add these sites you trust to your Trusted Sites zone. In an enterprise environment, we would leverage Active Directory Group Policy to do this. The way to add specific sites to a zone is well-documented. In short, we use the Sites to Zone Assignment List policy.

However, this doesn’t work with IE ESC turned on. This KB article hints at why. Although it says it applies to Windows Server 2003, I’m working with Windows Server 2016. My machine will be a Remote Desktop host and I want to lock it down. So, how can we keep IE ESC on and allow a specific list of sites to have looser security settings?

It seems there’s two ways this could work. In both cases, we still configure the Sites to Zone Assignment List:

1. Apply the Method 2 workaround listed in the KB article above. You may have to create the keys that are not present.

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2. This one is much more complicated. We will configure the EscDomains registry key. This key is described in a support article:

The EscDomains key resembles the Domains key except that the EscDomains key applies to those protocols that are affected by the Enhanced Security Configuration (ESC). ESC is introduced in Microsoft Windows Server 2003.

We can use Group Policy Registry Settings to update the registry. Enter the values in HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\CurrentVersion\Internet Settings\ZoneMap\ESCDomains.  Once completed, it will look something like the below:

Group Policy view:

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Registry view:

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Regardless of method, you can load up one of your sites and click File, Properties. The Zone should show “Trusted Sites.”

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One note, this machine also has other Group Policies applied from the Microsoft Security Guidance blog and other policies may change the behavior. Is there a better way? I don’t know, you tell me, comments below.

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