The Securities and Exchange Commission (SEC) is a governmental regulatory agency established by Congress which polices the practices of the securities industry.
Since 1934, the SEC's mission has been to protect investors and the market from malfeasance. FINRA (the 2007 successor to the NASD which was formed in 1939) is a self-regulatory organization in the industry which seeks to keep member firms more than compliant with SEC regulations.
Some of the specific things the SEC looks for are insider trading, inappropriate marketing practices, and investor protection issues.
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