The SEC.gov website has a blurb on Insider Trading. They start off with legal insider trading, when officers, directors and employees buy and sell stock in their own companies. Corporate insiders are required to report their trades.
Illegal insider trading “refers generally to buying or selling a security, in breach of a fiduciary duty or other relationship of trust and confidence, while in possession of material, nonpublic information about the security. Insider trading violations may also include “tipping” such information, securities trading by the person “tipped,” and securities trading by those who misappropriate such information.”
Under Rule 10b5-1, a person is trading on the basis of material nonpublic information if a trader is “aware” of the material nonpublic information when making the purchase or sale. The rule also sets forth several affirmative defenses or exceptions to liability. The rule permits persons to trade in certain specified circumstances where it is clear that the information they are aware of is not a factor in the decision to trade, such as pursuant to a pre-existing plan, contract, or instruction that was made in good faith.
Rule 10b5-2 focuses on the misappropriation theory of insider trading and how it applies to certain non-business relationships. This rule provides that a person receiving confidential information under circumstances specified in the rule would owe a duty of trust or confidence and thus could be liable under the misappropriation theory.