Ms. Best, 32, who has published at the investigative site MuckRock and elsewhere, noted that the Distributed Denial of Secrets site already hosts thousands of leaked documents from dozens of countries, the largest number from the United States.

The new site operates roughly on the model pioneered by WikiLeaks — inviting hackers and whistle-blowers to send confidential documents for posting. But Ms. Best has been quite critical of that site and its founder, Julian Assange, who played a central role in distributing the Democrats’ emails that Russians hacked in 2016. Distributed Denial of Secrets has posted a large archive of internal documents from WikiLeaks itself.

“Personally, I am disappointed by what I see as dishonest and egotistic behavior from Julian Assange and WikiLeaks,” Ms. Best said. But she added that she had made the Russian document collection available to WikiLeaks ahead of its public release on Friday, and had posted material favorable to Mr. Assange leaked from the Ecuadorean Embassy in London, where he has lived for more than six years to avoid arrest.

Russian and Eastern European hackers have for many years been among the world’s most active, many operating, initially, from a criminal underground in search of profit. But over the last decade, Russian intelligence agencies have become adept at using cyberintrusions to pilfer documents abroad as part of intelligence gathering and to leak for political purposes.

While the 2016 American election attack, carried out by Russian military intelligence hackers from the agency known as the G.R.U., has gotten the most attention, similar hack-and-leak operations have been carried out on a daily or weekly basis for years in Eastern Europe. Ukrainian hackers have worked aggressively to expose Russian covert activities in Crimea and the regions of eastern Ukraine controlled by separatist rebels.

Business tycoons have used hackers to go after rivals. Activists have sought to expose wrongdoing by the police and security agencies. The resulting archives of emails and inside documents have been posted all over the web, and the new collection seeks to gather it all in one place.

Ms. Best said Distributed Denial of Secrets is operated by fewer than 20 people who live in multiple countries, most preferring to remain anonymous. She said the Russian project began last year when she connected with a journalist looking for a collection of emails hacked by Shaltai Boltai, the Russian group whose name means Humpty Dumpty.