When PSTN is completely replaced with VoIP, secure phone call is relatively easily guaranteed by strong authentication and encryption. However, what we can do now to technically block only illegal robocalls is limited. Thus, the best possible way to dramatically reduce illegal robocalls is to block the definitely illegal robocalls and to help identify the possibly illegal robocalls and let law enforcement deal with the illegal robocallers. On the network side, from the fact that most robocallers use VoIP to make phone calls from outside of the US and spoof caller IDs or caller addresses (telephone numbers), the international calls which come from overseas but have US local caller addresses have a possibility of illegal robocalls. Those calls should be blocked unless those caller numbers match with the numbers on the white lists. The signaling information of those calls needs to be recorded. If a company wants to use overseas call center and keep the US caller IDs, those caller numbers need to be registered at the FTC and white lists need to be maintained and compared with the possibly spoofed caller numbers. On the callee’s side, when you receive an illegal robocalls, you can file a complaint to FTC. Then if FTC can match your complaint with one of the recorded possibly illegal robocall’s information, its signaling information may help identify the illegal robocaller.