Three Chinese nationals face federal charges for allegedly hacking into two major U.S. law firms in a scheme to trade on information about imminent mergers and acquisitions.

U.S. Attorney Preet Bharara of the Southern District of New York announced Tuesday that Iat Hong, Bo Zheng and Hung Chin have been charged with infiltrating the servers of two law firms in 2014 and 2015 and accessing nonpublic information about pending deals. According to Bharara’s office, the information was used in trades that reaped roughly $4 million in illegal profits.