US prosecutors have secured their first conviction in a case involving hack attacks on three of the major financial news release publishers.
Alexander Garkusha pleaded guilty to conspiracy to commit wire fraud, in a New York court.
He admitted making $125,000 (£84,000) from trades made over a three-month period using information gleaned from stolen embargoed press statements.
It is alleged a total of $100m was earned by a wider group using the scam.
The US authorities first made their suspicions public in August, saying that they believed the computer servers of Business Wire, Marketwired and PR Newswire had been breached leading to the theft of more than 150,000 news releases.
Companies often issue details of their financial results and other market sensitive news to the companies in advance so that the information can be released to all their investors at a specific time.
Nine people have been charged by district attorneys in New York and New Jersey in relation to the case, but dozens of others have also named as being suspects.
The gang responsible for the hack is thought to be based in Ukraine. Other individuals accused of being involved live in Russia, France and Cyprus.
Georgia-based Garkusha agreed to co-operate with the authorities and give up his earnings as part of his plea. Other defendants have plead not guilty.
Garkusha is due to be sentenced on 6 May.