List of malicious underground forums required for non-malicious purpose

I came across an article, Tales of the Cyber Underground: Inside the Underground Ransomware Market

I found it very interesting and out of curiosity I want to look into such forums my self. I googled and found a page, http://ift.tt/1zljIVP

But most of the sites on above page are either not accessible or not interesting enough. Can any one give me links of some active and interesting underground forums.