"The recipients answer calls from national numbers but, on the other end, no one answers", the alert states, revealing that the receipt of "silent phone calls" has been very frequently reported to the Public Prosecutor's Office.

"When the recipient of the call answers, there is no answer on the other end, and a few seconds later the call drops", reports the Office, noting that if the recipient of the call does not answer and later returns it, the latter is answered by a person in national territory, a customer of a national operator and the true holder of that number forged by the action of criminal agents.

This last person "did not make the call in question, nor does he know anything about it. The real owner of the number has no knowledge that his number was abusively used to make a multitude of calls".

The Cybercrime Office states that "the details of this criminal activity are not yet fully known", but "there is already enough information to allow us to conclude that this type of (silent) phone calls are exploratory, intended to confirm or deny the validity of the telephone numbers called".

In its opinion, they are "a preparatory procedure for other telephone frauds, of which there is already extensive knowledge, whether by means of false police calls or written messages demanding payment".

Other scams

In addition to this phenomenon, and in parallel, the Cybercrime Office says it has identified, in this case, "clearly", another campaign of telephone scams targeting recipients in Portugal, in which the fraudulent calls are mostly conducted in English, "sometimes at a rudimentary level and with an accent commonly used in the Indian subcontinent".

In one of these schemes involving fraudulent calls, the criminal agent claims to be an employee of a cryptocurrency portfolio management entity and informs the victim that their email address is associated with a very old cryptocurrency wallet, where a very considerable amount of money is deposited. It also says that this wallet has been inactive for too long and, therefore, will be closed. Finally, it adds that this closure can be avoided if its owner (the victim) opens an account with another entity, to which the amounts in the wallet can be transferred.

The Cybercrime Office also states that cases have been identified in which the criminal agent provided the victim with instructions and credentials to access an online platform where the balance of the alleged digital wallet could be checked.

If, during the call, the victim offers to open a new account or wallet, as proposed by the criminal agent, the latter informs the victim that opening the account involves the immediate deposit of an amount that could reach hundreds of euros into the new account.

To this end, the criminal agent gives the victim precise instructions on how to transfer funds to this alleged new cryptocurrency wallet.

“This is, of course, a wallet controlled by the criminal agents, who, once in possession of the money, disappear,” it warns.

“These phone calls are fraudulent. They are made by criminal agents who are part of international organised crime groups. The sole purpose of the calls is to persuade victims to transfer monetary amounts to the cryptocurrency wallet that they indicate to them,” concludes the Cybercrime Office.