A new analysis suggests that 74% of all money made through ransomware attacks in 2021 went to Russia-linked hackers.
Researchers say more than $400 million worth of crypto-currency payments went to groups "highly likely to be affiliated with Russia".
But Russia has denied accusations that it is harbouring cyber-criminals.
Chainalysis, the group which carried out the research, said it was able to follow the flow of money to and from the digital wallets of known hacking groups.
Analysts say they know which hacking groups are Russian because they display various characteristics, for example, the gang is linked to Evil Corp - an alleged Russian cyber-crime group wanted by the US.
The research is further evidence that many cyber-criminal groups operate either in Russia or in the surrounding Commonwealth of Independent States - an intergovernmental organisation of Russian-speaking, former Soviet countries.
The US has also successfully retrieved millions of dollars from the digital wallets of multiple ransomware criminals.