While the Russians accused of attacking Mrs. Clinton's campaign also used traditional currencies, the prosecution claimed that they "used mainly Bitcoin when they were buying servers, registering domains and otherwise making payments to support hacking."
Bitcoin, added the accusation, "allowed the conspirators to avoid direct relations with traditional financial institutions, allowing them to escape a more thorough check of their identities and sources of funding."
The Russians have taken several steps to obscure their Bitcoin transactions, according to the prosecution. They bought some Bitcoins on so-called peer-to-peer exchanges, where buyers and sellers could interact directly without exchanges, collecting details on both sides.
The Russians have also created bitcoins through the process known as mining, the prosecution said. With mining, computers compete to unlock new Bitcoins by solving complex computational problems. This requires expensive equipment and lots of electricity, but apparently it was not an obstacle for the Russians.
The agents used Bitcoins to pay for much of the computer infrastructure used in hacking attacks, he said. This included payments for a server in Malaysia that housed dcleaks.com and money sent to a Romanian company that registered the domain name.
In March 2016, the prosecution said that the Russians also used Bitcoin to buy a so-called virtual private network account that allowed them to obscure their Internet protocol address and their position when they went online. They used that VPN account to manage a Twitter account known as Guccifer_2, which became famous after releasing some of the stolen emails from the Democratic National Committee and the president of the Clinton campaign, John D. Podesta.
The Russians also used Bitcoin to pay for servers from which they launched malware campaigns and "spearphishing" attacks against the National Democratic Committee, according to the prosecution. In those attacks, he said, the Russian agents took over the e-mail accounts of American officials.