SCADA security expert Joe Weiss, concerned about the lack of timely notification of threats to infrastructure, remains skeptical of latest DHS statements. In a followup WashPo article, Ellen Nakashima writes, "Weiss said that federal officials were seeking a degree of proof impractical for such a cyberattack. The control system at the Illinois plant probably does not log signals sent to the water pumps and, as a result, would contain no data on who might have gained access to the system, he said. 'Control systems don’t have that kind of logging'.” Weiss also points out his comments have been based on formal statements of disclosure from Illinois State Terrorism and Intelligence Center.
There doesn't exist a clear trail that can be documented to prove a cyberattack or where it originated. It's also clear from articles that the Illinois utility "suffered intrusions".