You'll have to excuse my ignorance on politics/government, but under a more libertarian/less government rule who is it that prevents this type of situation from

You'll have to excuse my ignorance on politics/government, but under a more libertarian/less government rule who is it that prevents this type of situation from occurring? That is, who ensures that sophisticated financial fraud does not occur? Assuming a small government, would it just be individual whistle blowers up against corporations in court?