Querying ArcGIS Server log files returns untrusted font warnings

Description

A warning log message indicating 'Invalid embedded font encountered' displays when querying ArcGIS Server logs in certain Windows deployments of ArcGIS Enterprise.

This log message can list any published service as a source, including the Sample Cities map service. While this warning does not affect the performance of services, it can fill up log files with unnecessary clutter.

Cause

The network in which ArcGIS Enterprise is installed does not trust certain fonts used in Esri software. Untrusted fonts are any font installed outside of the C:\Windows\Fonts directory, but this setting can be updated by network administrators to include fonts used in other products. 

Additionally, the network can be configured to ignore untrusted fonts through a Group Policy or Registry Key setting, and these rules can be enforced across all machines in the network.

Note: 
This warning message is related entirely to an organization's network settings, and does not affect the performance of Esri software in any way. This message is only returned when using an unsupported Microsoft setting to enforce Group Policy settings over a network.

Solution or Workaround

Note:
The following workaround may require the assistance of an organization's System Network Administrator.

To circumvent this issue, add the fonts used in Esri software to the trusted directory: C:\Windows\Fonts. Alternatively, disable the relevant Group Policy/Registry Key setting from the network. For more information on managing fonts via Group Policy and Registry Keys, refer to Microsoft: Block untrusted fonts in an enterprise

Note:
For security, Microsoft recommends that the Group Policy setting to enable Untrusted Font Blocking not be used.