Using a unique dataset of fake stock promotion articles prosecuted by the Securities and Exchange Commission, we examine the impact of fake news. In addition, we use a linguistic algorithm to detect deception in expression for a much larger set of news content using the fake articles as a training sample. We find increased trading activity and temporary price impact from fake news about small firms, but no impact for large firms. Using the SEC investigation as a shock to investor awareness of fake news, we find a marked decrease in reaction to news, particularly content deemed less authentic, but also legitimate news. These findings, including the indirect spillover effects on other news, are most pronounced for small firms with high retail ownership and for the most circulated articles. Understanding the motivation behind the fake articles, we find that small firms engage in corporate actions and insider trading designed to profit from the fake articles, consistent with concerns of coordinated stock price manipulation. No such patterns are observed for large firms. The setting offers a unique opportunity to quantify the direct and indirect impact of fake news.