A MARTÍNEZ, HOST:

There are nearly 35,000 defectors from North Korea living in South Korea. Many of them rely on a secretive network of brokers to check on their families back home or to send them money when their families really need it. A broker's job has been dangerous and difficult as North Korea tightened its border control, but now another threat has emerged, this time in South Korea. Here's NPR's Se Eun Gong.

UNIDENTIFIED PERSON: (Laughter, speaking Korean).

(SOUNDBITE OF DOG BARKING)

SE EUN GONG, BYLINE: Over the sound of the TV and a dog's bark, a middle-aged woman is quietly counting a bundle of cash in a phone video. This video is proof of delivery filmed by an unnamed courier.

(SOUNDBITE OF ARCHIVED RECORDING)

JU SU-YUN: (Non-English language spoken).

UNIDENTIFIED COURIE

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