Although the United States cracked down on terrorist financing after the 9/11 attacks, instability in the financial system, like the Argentine debt default in 2001, continued to give banks an incentive to look the other way. My reporting on the ’Ndrangheta, the powerful criminal syndicate based in Southern Italy, found that much of the money laundering over the last decade simply shifted from America to Europe. The European debt crisis, now three years old, has further emboldened the mob.

IN Greece, as conventional bank lending has gotten tighter, more and more Greeks are relying on usurers. A variety of sources told Reuters last year that the illegal lending business in Greece involved between 5 billion and 10 billion euros each year. The loan-shark business has perhaps quadrupled since 2009 — some of the extortionists charge annualized interest rates starting at 60 percent. In Thessaloniki, the second largest city, the police broke up a criminal ring that was lending money at a weekly interest rate of 5 percent to 15 percent, with punishments for whoever didn’t pay up. According to the Greek Ministry of Finance, much of the illegal loan activity in Greece is connected to gangs from the Balkans and Eastern Europe.

Organized crime also dominates the black market for oil in Greece; perhaps three billion euros (about $3.8 billion) a year of contraband fuel courses through the country. Shipping is Greece’s premier industry, and the price of shipping fuel is set by law at one-third the price of fuel for cars and homes. So traffickers turn shipping fuel into more expensive home and automobile fuel. It is estimated that 20 percent of the gasoline sold in Greece is from the black market. The trafficking not only results in higher prices but also deprives the government of desperately needed revenue.

Greece’s political system is a “parliamentary mafiocracy,” the political expert Panos Kostakos told the energy news agency Oilprice.com earlier this year. “Greece has one of the largest black markets in Europe and the highest corruption levels in Europe,” he said. “There is a sovereign debt that does not mirror the real wealth of the average Greek family. What more evidence do we need to conclude that this is Greek mafia?”

Spain’s crisis, like Greece’s, was prefaced by years of mafia power and money and a lack of effectively enforced rules and regulations. At the moment, Spain is colonized by local criminal groups as well as by Italian, Russian, Colombian and Mexican organizations. Historically, Spain has been a shelter for Italian fugitives, although the situation changed with the enforcement of pan-European arrest warrants. Spanish anti-mafia laws have also improved, but the country continues to offer laundering opportunities, which only increased with the current economic crisis in Europe.

The Spanish real estate boom, which lasted from 1997 to 2007, was a godsend for criminal organizations, which invested dirty money in Iberian construction. Then, when home sales slowed and the building bubble burst, the mafia profited again — by buying up at bargain prices houses that people put on the market or that otherwise would have gone unsold.

In 2006, Spain’s central bank investigated the vast number of 500-euro bills in circulation. Criminal organizations favor these notes because they don’t take up much room; a 45-centimeter safe deposit box can fit up to 10 million euros. In 2010, British currency exchange offices stopped accepting 500-euro bills after discovering that 90 percent of transactions involving them were connected to criminal activities. Yet 500-euro bills still account for 70 percent of the value of all bank notes in Spain.