Also, consider the audience—the story should be appropriate for a general audience, so maybe not too graphic in describing criminal activities. Emphasize the consequences rather than the methods.
Avoid making it too technical so it remains accessible, but include enough detail to show authenticity. Maybe add a twist where the protagonist finds a way to infiltrate the forum or stop the flow of stolen data.
I should also think about the themes—privacy, corporate responsibility, the dark web's role in cybercrime. Maybe a moral dilemma for the protagonist: exposing the forum could put many at risk or lead to better security measures.