SIM Swapping, phishing, smishing…
In a recent case decided by the Supreme Court (STS 571/2025), an unfortunately increasingly common situation was addressed: a customer saw his bank account emptied through transactions he had not authorized. The ruling sets an important precedent in favor of electronic banking users.
The victim, an Ibercaja customer, suffered what is known as “SIM swapping”. This type of fraud allows criminals to duplicate the SIM card of the victim’s cell phone and thus receive the verification codes needed to make transfers. Although the customer had already warned the bank weeks before about suspicious movements and had requested security measures, the bank did not react.
In a single night, 15 transfers were made from his account totaling more than 83,000 euros, without the bank’s system detecting any anomaly. Worse still: it was another bank that alerted of a possible fraudulent operation. Not Ibercaja.
Both the Court of First Instance and the Provincial Court of Zaragoza convicted the bank, and now the Supreme Court has confirmed that conviction, reaffirming that:
- The bank must act with a high level of diligence in the detection of anomalous operations.
- It is not enough to prove that the transaction was technically authenticated (e.g. with the SMS code).
- If the client denies having authorized a transaction, it is up to the bank to prove fraud or gross negligence on the part of the user. And in this case, it was not proven.
The Supreme Court has been clear: digital banking cannot hide behind the fact that the intended systems were used if there is no guarantee that this authentication really protects the user against sophisticated attacks.
What does this mean for the banking customer?
If you have been the victim of online fraud, and charges or transfers have been made from your account that you did not authorize, the bank may be obliged to return the money to you, unless it can prove that you acted with gross negligence.
And remember: if you have reported suspicious movements and the bank has not taken action, this is clearly in your favor.
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