A naked short sale is the illegal practice of short selling shares that do not exist. Typically, in short selling the trader must first borrow shares in order to sell them short. But with naked short selling there are no shares borrowed and so the short sale puts more short pressure on the stock that could be larger than the available tradeable shares. Naked short selling was made illegal in the wake of the 2008 financial crisis, but it still occurs at times due to loopholes in regulations and differences between electronic and paper trading systems.