Spam and silent calls rise through caller ID spoofing

Spam calls and silent calls are becoming increasingly common, often driven by automated dialing systems. These systems may dial multiple numbers simultaneously and hang up if no operator is immediately available. Such calls can also be used to verify if a phone line is active for future commercial or fraudulent purposes.

A prevalent technique used by scammers is “CLI spoofing,” or caller ID spoofing. This allows callers to manipulate the number displayed on a recipient's screen, often making it appear as a local or familiar number to increase the likelihood of the call being answered. This method is particularly effective with Voice over IP (VoIP) technology, where callers can manually enter any number to appear as the origin.

In Spain, while regulations have tightened, the issue has shifted from fake local numbers to calls originating from foreign countries. The technical difficulty in stopping these calls lies in the fact that traditional telephony protocols, such as SS7, were not designed to verify caller identity. Furthermore, there is currently no widespread cryptographic signature or verification mechanism among operators to confirm that a caller is authorized to use a specific number.