http://www.sec.gov/answers/insider.htm
"...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.
Examples of insider trading cases that have been brought by the SEC are cases against:
Corporate officers, directors, and employees who traded the corporation's securities after learning of significant, confidential corporate developments;
Friends, business associates, family members, and other "tippees" of such officers, directors, and employees, who traded the securities after receiving such information;
Employees of law, banking, brokerage and printing firms who were given such information to provide services to the corporation whose securities they traded;
Government employees who learned of such information because of their employment by the government; and
Other persons who misappropriated, and took advantage of, confidential information from their employers.
Because insider trading undermines investor confidence in the fairness and integrity of the securities markets, the SEC has treated the detection and prosecution of insider trading violations as one of its enforcement priorities.
The SEC adopted new Rules 10b5-1 and 10b5-2 to resolve two insider trading issues where the courts have disagreed. Rule 10b5-1 provides that a person trades 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 clarifies how the misappropriation theory 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.
For more information about insider trading, please read Insider Trading—A U.S. Perspective, a speech by staff of the SEC.
http://www.sec.gov/answers/insider.htm
