At least three different types of ransomware were used in the attacks.

The U.S. authorities said that over the past year, several cyberattacks on water supply and sewerage facilities using ransomware were carried out in the country.

The warning of the Cybersecurity and Infrastructure Security Agency (CISA) mentions a series of attacks in the period from September 2020 to August 2021, in which at least three different types of ransomware were used.

Such programs encrypt computer files and demand a ransom for their recovery.

When carrying out attacks on a water treatment plant in Maine three months ago and in California in August, the attackers bypassed computers and paralyzed Supervisory control and data acquisition (SCADA) that issue mechanical commands to equipment.

According to federal agencies, the Maine system had to be switched to manual control.

The March hack in Nevada also affected SCADA devices that provided operational control but could not issue commands.