The cyber slip-ups could allow hackers to take over or at least monitor devices, like pumps at a water treatment plant, or systems, like fire alarms in a building.
In more than 1,000 of these systems users didn't even need a password to commandeer it, Swedish Radio reports.
"What's so special about these systems is that they control often physical things which make our society work," Swedish Radio reporter Emil Hellerud says.
Hellerud says his reporting found, for instance, turbines at a wind farm that could be taken over remotely and forced to stop, causing expensive damage that would take a long time to repair.
Security experts tell Hellerud that greater awareness about the flaws can help fix them as well as thinking twice before connecting pieces of critical infrastructure to the internet.