The person suspected of being behind malware attacks known as "Carbanak" and "Cobalt" was arrested in Alicante, a port city on the south east coast of Spain, after cooperation between police forces in the United States, Asia and Europe, Europol said.
The Interior Ministry said 'Denis K.', who had directed the criminal organisation from Spain since 2013, was arrested with three members of his organisation, who originally came from Russia and Ukraine, it said.
The Ukrainian police did not provide further details.
Europol said the group had operated since 2013, with members in 40 countries, carrying out attacks on 100 financial institutions. They targeted bank employees with emails infecting their computers and then using them as a base to gain control of bank network and servers.
"With that level of access, the nefarious individuals authorise fraudulent bank transfers, raise the balances of mule accounts or command affected ATMs to spit out the money for them," Europol said.
Europol, said the U.S. Federal Bureau of Investigation, Romanian, Belarussian and Taiwanese authorities, and private cyber security companies were assisting in the case.
ORGANIZATION USED 'MULES' TO EXTRACT MONEY
The organisation needed the support of other criminal groups to coordinate the work of the 'mules' they used to extract money from cash points that they attacked, it said. Until 2015 they used the Russian mafia for this, and after 2016 the Moldovan mafia.
Their earnings were converted into bitcoins at exchange houses in Russia and Ukraine. These were later transferred to their accounts and they accumulated about 15,000 bitcoin, Interior Ministry said.
Denis K used financial platforms in Gibraltar and the United Kingdom to load prepaid cards with bitcoin and spend them in Spain on cars, homes, and other goods.
He also set up an "enormous network" to mine bitcoins which he used as a means of laundering money.
Get Breaking news, live coverage, and Latest News from India and around the world on NDTV.com. Catch all the Live TV action on NDTV 24x7 and NDTV India. Like us on Facebook or follow us on Twitter and Instagram for latest news and live news updates.