Here's an AP backgrounder on the tri-border area in South America:

...Such chaotic scenes give life to the city's reputation of lawlessness and U.S. officials' description of the tri-border area where Paraguay, Brazil and Argentina meet as a key South American point for Islamic terrorist fund raising to the tune of $100 million a year. Yet few arrests have been made or assets frozen, and local officials told The Associated Press they are ill-prepared to fully track financial movements and they discount terror links...

The tri-border area - also known as the "Muslim Triangle" - was last mentioned in "Illegals from terrorist nations are crossing the border into Arizona."