>If you are talking about IIS's FTP, you need to assign the rights in the Directory tab under IIS's Service Manager applet, and you need to assign the NT rights to the same file system directories. A user only has rights if both are set. If you are talking about the basic FTP (not IIS), I don't know this.
There is only a Directory Security tab. By default, all computers have accessed. Is this what you are talking about?