Very fast.
But, sometimes, curiosity gets the best of them. As it turns out, they abhor secrets; and, humans who keep them are fair game for inspection, anywhere, anytime.
As I prepared to capture more paranormal activity, a curious demonic entity peers into the light tunnel aperture (a peanut butter lid with a hole drilled through it) on the lens of my camera (my laptop), which sat on the floor while I made adjustments to the mount (a TV stand). Probably just to make sure I wasn't hiding something in there.
And, yes, they are really like that. Some demons will not attack a human unless they have already exerted some sort of influence on them prior by and through other entities. In my case, they use 'reptoids,' demonic entities that I call the Voices Demons, who can read every thought, and even cull some—but not all—memories from your mind. In all the ways this is useful to a demon, I don't know; but, it does keep good track of their prey, and helps them exert control over the emotions and actions of a target, which is key to cultivating a viable demonic host.