The ease with which bad actors can find a worldwide market for malicious apps that spy on people’s digital devices is at the center of an Australian Federal Police case against a man who, starting at the age of 15, wrote a stalkerware application and sold it to 14,500 people in 128 countries....

Australian police last month arrested the man, now 24, and identified at least 201 of his Australian customers, in an investigation that began in 2017 and involved a dozen law enforcement agencies in Europe and Australia, and information provided by Palo Alto Networks and the FBI. The case underscores the sheer scope of the market for stalkerware—the app, costing just $35, was sold for seven years before law enforcement shut it down. Tens of thousands of victims were spied on, police said. Its customers included domestic violence perpetrators and even a child sex offender.