The illegal practice of short selling shares that have not been affirmatively determined to exist. Ordinarily, traders must borrow a stock, or determine that it can be borrowed, before they sell it short. However, some professional investors and hedge funds take advantage of loopholes in the rules to sell shares without making any attempt to borrow the stock.
On Oct 29, 2003, the SEC implemented a new rule to ban naked shorting in order to protect thinly traded stocks that are vulnerable to aggressive short-selling which would cause the stock price to fall. Critics of the new rule argue that if naked-shorting had not taken place during the micro-cap crime wave of the 1990s, such stocks would have climbed even higher before they crashed. Thus, the SEC's action to ban naked-shorting eliminated the only market force against over-hyped, or even fraudulent, small-cap and micro-cap stocks.