The used a buffer overflow exploit in "fingerd" as one of its attack mechanisms.

The Morris internet Worm used a buffer overflow to exploit in "fingerd" as one of its attack mechanisms. A buffer overrun, overflow, or overwrite is a condition at an interface under which more input can be placed into a buffer or data holding area than the capacity allocated, overwriting other information. The buffer overflow type of attack has been known since it was widely used by Morris Internet Worm in 1988.

The answer is energy. the arrows are showing how exited and energized the stones are.