The truth about the app that 'fakes any phone number'

Fake call app on the App Store.

Recently, posts warning about an internet-based call creation app have been circulating on social media in Vietnam. Notably, this tool can be used to spoof the caller's number. On the recipient's device, the incoming call will appear as a name if the number is already saved in their contacts.

In fact, the ability to make virtual calls with custom phone numbers is part of the VoIP (Voice over Internet Protocol) tool. According to the FCC (Federal Communications Commission), caller ID spoofing exploits vulnerabilities in how traditional telecommunications networks (PSTN) communicate with VoIP protocols.

Virtual PBX software or a simple VoIP service provider offers the option to fill in any number in the From: field when initiating a call. In the next step, it's routed from the internet to the traditional mobile network. However, the tracking gateway often lacks a way to verify if the From: data field (representing the outgoing number) is legitimate. As a result, the network operator directly displays that phone number on the recipient's phone.

Changing Caller IDs isn't entirely prohibited. It's still used by large call centers to display a single phone number instead of the individual employee IDs. However, abusing this protocol for purposes of confusion or fraud is banned in many countries.

Neither Google nor Apple would tolerate software that deceives users or facilitates dishonest behavior, including the falsification of contact information for fraudulent purposes. Therefore, the existence of an application on the App Store that allows such services is alarming.

According to the description, the software doesn't directly mention spoofing phone numbers. It's advertised as a voice-changing feature for calls, intended for pranks and surprises. It's also a paid application, charging per minute of use.

In February 2025, Ms. PTH, residing in Cua Lo ward (formerly Nghi Huong ward, Vinh city, Nghe An province), was defrauded of nearly 700 million VND.

Specifically, the scammer used caller ID spoofing technology to make calls that displayed a phone number appearing to be the official number of the power company. Because the scammer repeatedly urged and threatened to cut off the electricity if payment wasn't made promptly, the woman complied with the scammer's demands, installing an application sent via Zalo that mimicked the power company's app, thereby installing malware on her phone.