NEW YORK — Several of the most popular Internet-connected baby monitors lack basic security features, making them vulnerable to even the most basic hacking attempts, according to a new report from a cybersecurity firm.

The possibility of an unknown person watching their baby’s every move is a frightening thought for many parents who have come to rely on the devices to keep an eye on their little ones. In addition, a hacked camera could provide access to other Wi-Fi-enabled devices in a person’s home, such as a personal computer or security system.

The research released Wednesday by Boston-based Rapid7 Inc. looks at nine baby monitors made by eight different companies. They range in price from $55 to $260.

The cameras are often mounted over a baby’s crib or another place where they spend a large amount of time. They work by filming the child, then sending that video stream to a personal website or an app on a smart phone or tablet. Some of the cameras also feature noise or motion detectors and alert parents when the baby makes a sound or moves.

The Rapid7 researchers found serious security problems and design flaws in all of the cameras they tested, says Mark Stanislav, a senior security consultant at Rapid7 and one of the report’s authors.

Some had hidden, unchangeable passwords, often listed in their manuals or online, that could be used to gain access. In addition, some of the devices didn’t encrypt their data streams, or some of their Web or mobile features, Stanislav says.

The problems with the cameras highlight the security risks associated with what’s become known as the “Internet of things.” Homes are becoming increasingly connected, with everything from TVs to slow cookers now featuring Wi-Fi connections. But many consumer devices often don’t undergo rigorous security testing and could be easy targets for hackers.

And if a hacker has access to one connected device, he or she could potentially access everything tethered to that home’s Wi-Fi network, whether it’s a home computer storing personal financial information or a company’s computer system that’s being accessed by an employee working from home.

In the Rapid7 study, researchers rated the devices’ security on a 250-point scale. The scores then received a grade of between “A” and “F.” Of those tested, eight received an “F.”