Veolia Environnement SA, the French utility that provided drinking water to 100 million people last year, has beefed up cyber security to protect installations from hackers.

“Cyber crime is the main threat for the company,” Jean-Louis Fiamenghi, the head of security at the Paris-based water, waste and energy company, told journalists Tuesday. “There’s been some attempts, but they aren’t always villainous. Some hackers are lured by the challenge. We haven’t been asked for ransoms.”

Veolia has also added new sensors that can detect a much wider range of poisons than previous monitoring systems in some of its networks, the security chief said. At this stage, it hasn’t detected criminal or terrorist attacks, and illegal intrusion attempts at its facilities have mostly been made by juveniles, he said.

Veolia is one of 250 companies deemed “critical” by the government that have heightened security measures. More than 200 people have been killed in a string of terrorist attacks across France since January 2015.