Epic Games’ “Gears of War 3” was hacked by a team of hackers known as the “Xbox Underground” along with other firms as well as the U.S. Army, and two men pleaded guilty in the case on Tuesday.

The hacking ring stole more than $100 million in intellectual property, according to federal prosecutors. The guilty pleas were disclosed Tuesday in federal court in Delaware. Other indictments also were announced.

Targets included Xbox One and Xbox Live software and data, Call of Duty: Modern Warfare 3 and Gears of War 3, and Apache helicopter simulation software.

Gears of War 3 launched in September 2011. Epic later sold the entire Gears franchise to Microsoft.

A press release from the Justice Department outlined the details:

“Specifically, the data cyber-theft allegedly included source code, technical specifications and related information for Microsoft’s then-unreleased Xbox One gaming console; intellectual property and proprietary data related to Xbox Live, Microsoft’s online multi-player gaming and media-delivery system; Apache helicopter simulator software developed by Zombie Studios for the U.S. Army; a pre-release version of Epic’s video game, ‘Gears of War 3;’ and a pre-release version of Activision’s video game, ‘Call of Duty: Modern Warfare 3.’ The defendants also allegedly conspired to use, share and sell the stolen information.”

David Pokora, 22, of Mississauga, Ontario, and Sanadodeh Nesheiwat, 28, of Washington, New Jersey, each pleaded guilty to a single count of conspiracy to commit computer fraud and copyright infringement. They face up to five years in prison when sentenced in January.

An 18-count superseding indictment that was returned by a grand jury in April and unsealed Tuesday also charges Nathan Leroux, 20, of Bowie, Maryland, and Austin Alcala, 18, of McCordsville, Indiana, with participating in the conspiracy. An Australian national whose name was not released also has been charged, and authorities, who are continuing their investigation, say roughly half-a-dozen other individuals may be involved.

“Sophisticated Hackers”

“These were extremely sophisticated hackers…. Don’t be fooled by their ages,” Assistant U.S. Attorney Ed McAndrew said after Tuesday’s court hearing.

At the same time, McAndrew said, their method of compromising the computer systems of the companies was relatively basic: stealing the computer user names and passwords of employees and software development partners.

Once inside the companies’ computer networks, the conspirators accessed and stole unreleased software, software source code, trade secrets, copyrighted and prerelease works, and other information, authorities said. They also stole financial and other sensitive information relating to the companies, but not their customers, McAndrew told U.S. District Court Judge Gregory Sleet.

Prosecutors said the ring’s exploits included manufacturing and selling a counterfeit Xbox One gaming console before the unit’s official release and gaining access to an Army computer system for two months in late 2012 through their hacking of Zombie Studios, a Seattle-based video game company that was working with the Army on flight simulation software to train Apache helicopter pilots.

“As soon as they were notified, they addressed the particular manner in which they were branched,” McAndrew said when asked about the military’s response to the hacking.

McAndrew said FBI officials in Delaware were alerted to the hacking operation in January 2011 by a confidential informant, and that the gaming companies cooperated in the investigation. Authorities began obtaining arrest warrants last year, and Pokora, who McAndrew said was looked to by other group members as a leader, was taken into custody in March at a border crossing in Lewiston, New York.

Pokora’s plea is believed to be the first conviction of a foreign-based individual for hacking into U.S. businesses to steal trade secret information, authorities said.