An over-the-counter security is not traded on an exchange, usually due to an inability to meet the major exchange's listing requirements. For such securities, brokers negotiate directly with one another over computer networks and by phone, and their activities are monitored by the National Association of Securities Dealers (NASD). OTC stocks are high-risk, since they are not considered stable enough to trade on a major exchange. They also tend to trade infrequently, making the bid vs. ask spread larger. Research about these stocks is also more difficult to obtain, as their filings are not public.