If you purchased the securities of a company that is involved in a class action (usually as a named defendant) during the specified class period, then you are automatically considered a member of the class, even if you do not retain a law firm to prosecute claims on your behalf.
The concept of class membership also applies to consumer fraud class actions and antitrust class actions. For example, if you purchased a product from a company that is alleged to have engaged in improper marketing practices during a certain time period (the class period), you would be a member of a consumer fraud class, even if you did not personally retain an attorney.
