Life in prisons is regulated by "vorovskye zakony"- "thief law", an oral collection of traditions, some of which go back to the times of the tsars. This "law" is interpreted by the highest of the four "suits" (castes) - the "blacks" or "thieves". There is a further elite to be found inside of this elite comprised of "established" or "legalised thieves" (vory v zakone), these represent the very top of the criminal underworld, and number only a few hundred in the whole of the former Soviet Union.  More images here