
The first in-depth analysis of North Korea's internal computer operating system has revealed spying tools capable of tracking documents offline.
Red Star OS was designed to superficially mimic Apple's OS X, but hidden features allow it to watermark files and tie them to an individual.
The covert tools were discovered by two German researchers who conducted the analysis over the past month.
They presented their findings at the Chaos Communication Congress on Sunday.
Florian Grunow and Niklaus Schiess pored over the code of Red Star OS version 3.0, which first surfaced online about a year ago.
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The system's coders "did a pretty good job" of mimicking the basic design and functionality of Apple computers, Mr Grunow tells, but with a twist.
Any files uploaded to the system via a USB stick or other storage device can be watermarked, allowing the state to trace the journey of that file from machine to machine. Red Star can also identify undesirable files and delete them without permission.