Digital assistants such as Apple’s Siri, Google Now and the device Amazon Echo are designed to respond when you speak to them. But to accomplish this, these high-tech helpers must monitor what you’re saying, though digital assistants are not supposed to respond unless you say a particular phrase—“Hey, Siri” on the latest iPhones…“OK, Google”…or “Alexa” for Amazon Echo.

Some people find it a bit creepy that something is monitoring every word we say. And ­security experts have uncovered a sneaky trick that a hacker could in theory use to send commands to your phone if you use Siri or Google Now (though the hacker would have to get within 16 feet of your phone).

If you find it unsettling that a device might be eavesdropping, you can stop these digital assistants.

Siri. To turn off Siri, enter the Settings menu of your Apple device. Select “General,” then “Siri,” then change the setting to off.

Amazon Echo. To turn off Echo, simply press the microphone on/off button on the top of the device. The LED light will turn red. Echo will not listen until the button is pressed again, turning the light blue.

Google Now. How you turn it off depends on the device…

In the Chrome web browser or on a Chromebook computer, click the three-horizontal-line icon (“hamburger menu”) near the upper-right corner of the screen. Select “Settings”…then under “Search,” look for “Enable OK Google” to start a voice search. If the small box next to this is checked, uncheck it.

On an Android device, select the “Google Settings” app (its icon is gray and contains a “g”). Choose “Search & Now,” then “Voice,” followed by “OK Google Detection.” If it currently says “On,” tap it once to turn it off.

On an Apple device, select the Google app (its icon is either a blue box containing a “g” or a white circle containing a multicolored “G”). Touch your profile picture in the upper-left corner, then “Voice Search.” If the box next to “OK Google” is checked, touch it once to turn it off.