An Internal Worker is a stereotype of a class that is specified in UML Extensions for Business Modeling. It can be shown as a regular class rectangle with stereotype of "internal worker", or as this icon:
Definition
An Internal Worker is a Worker that interacts with other workers and entities inside the system.
Drawing an Internal Worker
To draw an "internal worker" on a Use Case diagram, select the Worker icon from the tools menu, then opening the class definition and changing the stereotype from Worker to "internal worker".