A filter designed to weed out bozos. Usually a kill file on an e-mail system or similar, which automatically discards without notification any incoming from the designated bozo.
Extended here to a test on a website that filters out anyone unsuitable for job interview: "Hiring was a black hole," Cooper says. "I don't talk to bozos anymore because 90% of them turn away when they see our test. It's a self-administering bozo filter."
Term possibly originated by Scott Adams, who averred that he meant no disrespect to the actual Bozo the Clown, and would be delighted to receive e-mail from him.