Vladimir Drinkman, a 34-year-old Russian national, has pleaded guilty in a U.S. federal court case involving his role in the hacks of Nasdaq, Dow Jones, JC Penney Co. Inc., JetBlue Airways Corp., 7-Eleven Inc. and other major American enterprises. Drinkman admitted to being a member of a worldwide ring engaged in a scheme that ultimately netted more than 160 million credit-card numbers.

Federal attorneys in New Jersey who charged Drinkman with conspiracy charges involving wire fraud and unauthorized access to protected computers said the case was the largest to ever be prosecuted on U.S. soil. They alleged American companies and individuals lost more than $300 million because of the date breaches. Drinkman was arrested in the Netherlands and extradited to the U.S. this year.

“Defendants like Vladimir Drinkman, who have the skills to break into our computer networks and the inclination to do so, pose a cutting edge threat to our economic well-being, our privacy and our national security,” U.S. Attorney Paul J. Fishman of the District of New Jersey said in a statement Tuesday.

Drinkman and his cohorts, a number of whom remain at large, would monitor the computer networks of target companies for months, scanning for vulnerabilities in their Structured Query Language, a specialized programming language. Upon finding a vulnerability, they would enter the system and install malicious software that vacuumed up corporate information and customer payment details. That data would then be sold on underground Internet forums.

Drinkman’s sentencing is scheduled for Jan. 15. He faces as many as 30 years in prison.