Do you mean the underground digital economy?
"Anywhere between 10,000 - 20,000 people are estimated to work in the underground economy in Russia."
Russia's a big place and presumably the underground economy includes for instance prostitution, which alone surely... don't you think? I mean, not to be vulgar, but in Britain alone I reckon there's more than that.
So I think you mean "the underground digital economy". Or something like that. But what about bootleg music and video, dirty pictures, ...
Maybe you mean the digital fraud "industry"?