Black list

A black list, as opposed to a white list, is a list of denied or disapproved people/companies/elements/anything. Elements not listed are innocent until proven guilty.

If an organization keeps a black list of software, titles on the list will be banned. (A school might black list KaZaA and ICQ).

If a spam filter keeps a black list, mail from the listed addresses will be filtered away.

"Black list" as a verb means put on a black list.