Ambush marketing is a marketing tactic where Company A hijacks the marketing campaign of Company B in order to steal attention. It was introduced in the 1980s and can be direct, aiming to deceive audiences, or indirect, taking advantage of another brand's event or marketing. While it can be cost effective and creative, ambush marketing has cons such as having a negative connotation, diminishing sponsor value, and possibly being unethical or illegal depending on the approach.