Federal officials have accused four men of hacking into computer networks of the U.S. military and Microsoft and stealing more than $100 million worth of software.

In an indictment unsealed Tuesday, the four are accused of stealing proprietary software used to train Apache helicopter pilots as well as source code and technical specifications related to the Microsoft (MSFT) Xbox One gaming console and games including "Call of Duty: Modern Warfare 3."

The FBI says the men conspired to "use, share and sell" the stolen information, and federal officials have already seized $620,000 in alleged proceeds from the scheme.

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The defendants are Nathan Leroux, 20, of Bowie, Md.; Sanadodeh Nesheiwat, 28, of Washington, N.J.; Austin Alcala, 18, of McCordsville, Ind.; and David Pokora, 22, of Mississauga, Ontario, Canada.

Pokora and Nesheiwat have already pleaded guilty to conspiracy to commit computer fraud and copyright infringement and are awaiting sentencing in January. Pokora's plea, the Justice Department said, "is believed to be the first conviction of a foreign-based individual for hacking into U.S. businesses to steal trade secret information."

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An attorney for Alcala said the defense team was "continuing with our discussions with the U.S. Attorney's office in the hopes of reaching a favorable resolution." Lawyers for the other three men could not be reached for comment.

The FBI says the scheme ran from January 2011 until March of this year. The group allegedly gained access to their targets by injecting malicious code into their networks and stealing user names and passwords from company employees.