"Flak" refers to negative responses to a media statement or program. Such responses may be expressed as phone calls, letters, telegrams, e-mail messages, petitions, lawsuits, speeches, bills before Congress, or other modes of complaint, threat, or punishment. Flak may be generated by organisations or it may come from the independent actions of individuals. Large-scale flak campaigns, either by organisations or individuals with substantial resources, can be both uncomfortable and costly to the media.

Advertisers are very concerned to avoid offending constituencies who might produce flak, and their demands for inoffensive programming exerts pressure on the media to avoid certain kinds of facts, positions, or programs that are likely to call forth flak. The most deterrent kind of flak comes from business and government, who have the funds to produce it on a large scale.

For example, during the 1970s and 1980s, the corporate community sponsored the creation of such institutions as the American Legal Foundation, the Capital Legal Foundation, the Media Institute, the Center for Media and Public Affairs, and Accuracy in Media (AIM), which may be regarded as organisations designed for the specific purpose of producing flak. Freedom House is an older US organisation which had a broader design but whose flak-producing activities became a model for the more recent organisations.

The Media Institute, for instance, was set up in 1972 and is funded by wealthy corporate patrons, sponsoring media monitoring projects, conferences, and studies of the media. The main focus of its studies and conferences has been the alleged failure of the media to portray business accurately and to give adequate weight to the business point of view, but it also sponsors works such as John Corry's "expose" of alleged left-wing bias in the mass media.

The government itself is a major producer of flak, regularly attacking, threatening, and "correcting" the media, trying to contain any deviations from the established propaganda lines in foreign or domestic policy.

And, we should note, while the flak machines steadily attack the media, the media treats them well. While effectively ignoring radical critiques (such as the "propaganda model"), flak receives respectful attention and their propagandistic role and links to corporations and a wider right-wing program rarely mentioned or analysed.