The retailers identified publically are TJX, BJ's Wholesale Club, OfficeMax, Boston Market, Barnes & Noble, Sports Authority, Forever 21 and DSW.
It's already known that one of the unidentified chains (which is one of the nation's largest retailers) was the first to detect the cyberthieves.
In a filing on Thursday, U.S. Attorney Michael Sullivan told U.S. District Court Judge William G. Young that "There is forensic and/or testimonial evidence that the defendant and his co-conspirators hacked into numerous other businesses, which have not yet been publicly identified." The filing did not specify how many of those businesses are retailers.
The filing added that "hundreds of banks were victimized and potentially victimized as stolen credit card information was fraudulently used. As of this juncture, the government has not identified that list of banking institutions by name."
The defendant who pled guilty is Damon Patrick Toey, 23, of Miami. He agreed to accusations of wire fraud, credit card fraud and aggravated identity theft. He was said to have aided Albert Gonzalez in running the crime ring. Gonzalez pleaded not guilty the same day.
According to a Boston Globe story, when Young asked him why he was pleading guilty, Toey said that federal prosecutors "have enough, other than what I'm pleading guilty to," on him, "that would make it a lot worse, in my opinion."