The arm of the US Treasury which tries to make sure information needed to fight financial crime is efficiently shared between all the agencies which need it. Its main task is processing suspicious activity reports (SARs) from financial institutions. But it also engages in research to generate intelligence reports about money laundering and terror funding.
Before 11 September, FinCEN had an unfortunate reputation for being months if not years behind in processing SARs. Its budget has been increased, but it still risks being overwhelmed by the sheer volume of reports it receives. This number has been greatly increased by new legislation.