MADRID - Spanish police on Monday confirmed the arrest in eastern Spain of a Ukrainian who is allegedly thought to have been the brains behind the theft of around $1 billion from banks around the world over a one-year period.

The arrest took place after a three-year investigation during which Spain's National Police collaborated with Europol and the US Federal Bureau of Investigation (FBI), as well as police in Belarus.

As well as the man arrested in Alicante, 15 other suspects have been arrested in the United Kingdom, Belarus, and Kazakhstan.

The man, described by police as a "computer genius", also had a Russian passport and had lived with his wife in Alicante since 2014 without drawing attention to himself.

The gang's method of "remote" bank robbery was via a massive number of e-mails, each of which included a file containing malware designed by the suspect to attack the banks.

The police explained in a press conference that the malware sent to the banks infected the banks' systems, allowing the criminals access to the programs operating the automatic teller machines (ATM machines) from which a member of the gang would then withdraw large amounts of cash.

Another way the organization was able to steal money was by using access to banking systems to modify the amount of money in the accounts and then to make transfers elsewhere.