Inmates in Philippine prisons are reportedly operating sophisticated criminal networks in Japan and South Korea using smartphones and encrypted apps. Law enforcement traced drug deals and robberies to these prisoners, revealing a new method of transnational crime.

The prison cell, it turns out, is no obstacle to running a criminal empire. All you need is a smartphone, an encrypted messaging app and an overwhelmed corrections system, even if it is thousands of kilometres away. That was the conclusion law enforcement officials in South Korea and Japan reached after tracing a string of drug deals, home invasions and brazen robberies to inmates already serving time in the Philippines. The cases exposed a darkly inventive new chapter in Southeast Asia’s...