Research involving human subjects, even passive observation of public online communities, requires Institutional Review Board (IRB) review at most US and European academic institutions. Dark web research sits at the intersection of several ethical considerations that IRBs examine carefully: potential harm to research subjects, researcher safety, data handling for sensitive information, and dual-use concerns about research that could provide operational information to malicious actors.
Make the case to your IRB based on the actual nature of the research. Passive observation of publicly accessible dark web content (forum posts, market listings, published announcements) generally qualifies for exempt or expedited review because it involves no interaction with subjects and the content is already publicly visible. Research involving any form of deception, account creation, or active participation in dark web communities requires full board review.
Document your data minimization plan: what specific data you will collect, how you will de-identify it, where it will be stored, who will have access, and how it will be disposed of when no longer needed for research. De-identification of dark web forum posts is complex because the original posts are pseudonymous but the pseudonyms themselves may be directly linkable to individuals in some cases. Consult with an IRB coordinator familiar with internet research ethics before finalizing your data plan.