I have the same question, does this mean the student has navigated away from the assessment screen to another tab or window? I am curious as there is no locking of the browser when students are taking the assessment.
@WilliamBishop and @RaderMa I have always understood it to mean Canvas captured the system details. You will see it at the start of almost every quiz in Canvas when a student starts the quiz.
I am not 100% sure why you see it during the progress of the exam like in the screenshot. It does look like it shows after long pauses of activity (again based off the screenshot) so maybe it is Canvas doing another check of the system.
I do know it is not students taking screenshots of the exam or anything like that.