The small, glowing energy-based life-forms of M4C-862 exhibited intelligent behavior. They could pass through solid matter, but an electromagnetic field could contain or repel them. Harmless at first, they later gathered in swarms and attacked SG-1 and the scientists at the research base, killing Dr. Thompson and forcing the others to evacuate. The change in their behavior from benign to violent may have been retaliatory due to the capture of one of their own, or caused by the effect of intense magnetic fields during the moon's orbit.
Episode Reference: Prodigy