From the article "Mandiant discovered that two sets of I.P. addresses used in the attacks were registered in the same neighborhood as Unit 61398’s building. “

From the article "Mandiant discovered that two sets of I.P. addresses used in the attacks were registered in the same neighborhood as Unit 61398’s building. “It’s where more than 90 percent of the attacks we followed come from,” said Mr. Mandia. The only other possibility, the report concludes with a touch of sarcasm, is that “a secret, resourced organization full of mainland Chinese speakers with direct access to Shanghai-based telecommunications infrastructure is engaged in a multiyear enterprise-scale computer espionage campaign right outside of Unit 61398’s gates.”"