[ramimac]

Are you asking from a career or technical perspective?

This report isn't particularly technically complex, a majority of this sort of leaked data is widely available on clearweb forums. The minority requires building relationships and/or paying and/or developing a reputation that gets you access to more exclusive forums or circles. You then have to regularly crawl those forums, and avoid identification of your crawlers (as the more exclusive forums/site watch out for that sort of activity pattern). Then you just index the data and can perform searches or analysis.

https://scylla.sh/ is a free example covering just breach data.

From a career perspective, this is a subset of threat intelligence. The more interesting companies in this space often are leveraging military-style HumInt to gain access to these marketplaces and data, and often have leadership from that sort of military or government background. Most folks I'd assume are just standard engineers however, as a majority of the work is probably not specific to "dark web monitoring for intelligence."