There have been more than 130 control system cyber incidents in water/wastewater utilities. Like Oldsmar and Discovery Bay, most of these incidents have occurred in small water utilities. Many of these incidents were not publicly disclosed, nor were the utilities required to disclose these incidents.
Additionally, some of the real cases that were made public were later discounted such as the 2011 Illinois Water Hack where a small water utility had a water pump damaged from remote access into the SCADA system from Russia.
Source: Control Global