The Department of Homeland Security on Friday warned that a system used by organizations around the world to manage millions of machines and devices over the Internet is vulnerable to attack from hackers.

The software system known as the Niagara Framework enables corporate, military, health-care and other users to remotely control or monitor medical devices, elevators, video cameras, security systems and a wide array of other sensitive operations.

In an alert, cybersecurity officials said Niagara users should immediately prohibit guest users, bolster passwords, cut off direct access to the Internet and take other steps to keep hackers from exploiting software flaws.