The SEC generally conducts investigations confidentially for two main reasons. First, the SEC can conduct investigations more effectively if they are not announced publicly. For instance, important documents and evidence can be destroyed quickly if people hear of an investigation. Second, investigations are kept confidential to protect the reputations of companies and individuals if the SEC finds no wrongdoing or decide they cannot bring a successful action against them. As a result, the SEC can neither confirm nor deny the existence of any investigation.
An investigation becomes public when the SEC files an action in court or in its internal administrative process.