The Grugq
Pseudonymous researcher who went from anti-forensics to exploit brokering and then became the scene's most quoted voice on operational security.
In the early-to-mid 2000s The Grugq gave talks on anti-forensics — hiding data and traces so that a forensic investigation turns up as little as possible. In 2012 he featured in a Forbes piece on the zero-day trade, photographed next to a bag of cash, as a middleman between exploit writers and government buyers. The photo became shorthand for a market that until then had mostly been discussed in whispers.
Later he became best known for writing and speaking about OPSEC: why hackers get caught (rarely because the crypto breaks, almost always because they talk too much) and how influence operations work. The advice is dry and uncomfortable, which is rather the point.