Science fiction writers have been letting readers in on this idea for quite some time. For example, a LucasFilms, the buzz droid from Revenge of the Sith has the following characteristics:

An insidious weapon unveiled by the Confederacy of Independent Systems during the later stages of the Clone Wars, buzz droids are tenacious saboteurs launched onto enemy starfighters via specialized missiles. When the missile achieves an optimum proximity to its target, it fragments to unleash a cloud of melon-sized metal spheres into the target's flight path. The spheres attach themselves to a target vessel, popping open to reveal an insect-like droid equipped with cutters and other tools of vandalism...

(From Star Wars Buzz Droid)

And here's the video:

In his 1995 novel The Diamond Age, science fiction author Neal Stephenson wrote about a similar swarm of devices tasked with surveillance and security - the dog pod grid:

Atlantis/Shanghai occupied the loftiest ninety percent of New Chusan's land area - an inner plateau about a mile above sea level, where the air was cooler and cleaner. Parts of it were marked off with a lovely wrought-iron fence, but the real border was defended by something called the dog pod grid - a swarm of quasi-independent aerostats...

These pods were programmed to hang in space in a hexagonal grid pattern about ten centimeters apart...
(Read more about Stephenson's dog pod grid)

Here's a description of what it sounded like when you encountered a space full of autonomous drone aerostats:

Each aerostat in the dog pod grid was a mirror-surfaced, aerodynamic teardrop just wide enough, at its widest part, to have contained a pingpong ball. These pods were programmed to hang in space in a hexagonal grid pattern, about ten centimeters apart near the ground (close enough to stop a dog but not a cat, hence "dog pods") and spaced wider as they got higher. In this fashion a hemispherical dome was limned around the sacrosanct airspace of the New Atlantis Clave. When wind gusted, the pods all swung into it like weathervanes, and the grid deformed for a bit as the pods were shoved around; but all of them eventually worked their way back into place, swimming upstream like minnows, propelling the air turbines. The 'bines made a thin hissing noise, like a razor blade cutting air, that, when multiplied by the number of pods within earshot, engendered a not altogether cheerful ambience...

You could walk through the grid whenever you chose by shoving a few pods out of the way— unless Royal Security had told the pods to electrocute you or blast you into chum. If so, they would politely warn you before doing it.