More than $1.7 billion worth of cryptocurrencies have been reported stolen over the years, and of that sum, it is estimated that the majority, about $1 billion worth, can be attributed to just two separate groups, the identities of which are still unknown, according to the Wall Street Journal. The report comes from the firm Chainalysis, which tracks cryptocurrency transactions. While previously the thinking was that such hacks were the work of talented amateurs, further analysis of funds stolen in hacks has led the firm to believe that the biggest players are in fact dedicated professional criminals. The firm said it does not know who these groups are, but has labeled them "alpha" and "beta," each with its own distinct behavior pattern. 

Alpha seems to be the bigger, more controlled organization, and is believed to be driven at least in part by nonmonetary goals. In contrast, Beta is believed to be smaller and less organized, and is focused entirely on money. While both transfer stolen cryptocurrencies between thousands of accounts to hide their trail, Alpha tends to do so right away, converting most of its loot into cash within about a month, Beta tends to wait longer, sometimes up to 18 months, presumably so publicity around the hack can fade. Once they feel the heat has died down, they immediately convert about 50 percent of their funds within a few days over a single exchange. 

The two groups, it is believed, are still active.