At the point when the syringe is removed the pump or the plunger clamp and tube is tampered with the 3300 will actually alarm. Otherwise, when the cover is opened, the pump operation is suspended (there is no alarm but this is normal operation).
I guess that access to the syringe is what is important to whoever opens the cover - so if the syringe is tampered with there will be an audible and visual alarm produced. That is unless the infusion is stopped after the cover is forced open (1 keypress and a confirmation keypress I think).
Either way this would be unauthorised tampering beyond the control of the manufacturer in my opinion. It's the control of the drug that is important - the pump does actually alarm if the syringe is tampered with while it's pumping - the cover makes unathorised access more difficult that's all (most manufacturers covers are perspex and can be broken open with relatively little effort).
