Authorities in Spain have arrested the leader of a cybercrime group behind the Carbanak and Cobalt malware attacks, which targeted over 100 financial institutions around the world. The mastermind behind this heist was allegedly an Ukranian national called Denis K. The operation was conducted in conjunction with Europol. The gang, composed of Russian and Ukranian nationals, would manage to gain access to bank servers and networks through a series of emails sent to employees, according to Europol. The emails would eventually infect their computers and target valuable security data such as passwords, resulting in the group gaining access to account balances which they changed and even gave instructions to ATMs to issue large quantities of cash. Authorities said the Cobalt malware alone allowed the cybercriminals to steal up to \u20ac10 million (U$12.4 million) per attack. In total, the group reportedly infiltrated banks in more than 40 countries, resulting in the loss of over \u20ac1 billion (US$1.2 billion). The group also managed to set up a cryptocurrency farm, which they use to launder money. According to Europol investigators, "The criminal profits were also laundered via cryptocurrencies, by means of prepaid cards linked to the cryptocurrency wallets which were used to buy goods such as luxury cars and houses." The mastermind behind the group, who was identified as Denis K, operated from Spain and had accumulated about 15,000 BTC worth about $120 million, authorities said. The operation to catch this gang was quite massive and involved the police from several countries including the United States, Taiwan in Asia and Romania in Europe. Denis K was eventually arrested in the Spanish port city of Alicante. The Spanish Interior Minister announced that three other gang members were arrested alongside a massive haul of jewels worth half a million dollars, two luxury cars and properties. Bank accounts belonging to the gang members were also frozen. According to a statement by Europol, the individuals authorized fraudulent bank transfers, adjusted mule bank accounts and commanded ATMs to issue cash. Apparently the group worked with the Russian mafia up till 2016 but then began working with the Moldovan mafia. This massive operation enabled the gangsters to accumulate a staggering 15,000 BTC with the money being converted on cryptocurrency exchanges in Russia and Ukraine which would later be transferred to the group's personal bank accounts. This is not the first time that cryptocurrency has been used to launder money. A Turkish gang was involved in extortion to the amount of 450 BTC from a Turkish businessman while in February a Taiwanese gang was arrested for the theft of BTC worth up to $100,000.