No service exists for handler 'CL_HTTP_EXT_CSIF'

What causes this issue?

There is no service available for the handler 'CL_HTTP_EXT_CSIF'.

System Response

HTTP access is refused.

How to fix this error?

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Procedure for System Administrators

If you need HTTP access, a service must be defined. Use transaction
<DS:TRAN.SICF>SICF</> to define a service with handler class
'CL_HTTP_EXT_CSIF'. Define a user and password for anonymous logon
and activate the service.

Error message extract from SAP system. Copyright SAP SE.