Banks, regulators and law-enforcement agencies are sharing more intelligence through voluntary networks to deter money laundering and terrorism financing. As the practice spreads, so do the risks of data mishandling, observers said.

Information-sharing partnerships are sprouting across the global financial landscape. The U.K. pioneered the practice in 2015, and new partnerships were launched in Singapore, the U.S. and Australia last year. The Netherlands, Hong Kong and law-enforcement agency Europol are running pilot programs...