Please read the whole article. It is very detailed.
Read more: Mandiant Report Chinese Hacking - Business Insider
Additionally, publishing certain kinds of indicators dramatically shortens their lifespan. When Unit 61398 changes their techniques after reading this report, they will undoubtedly force us to work harder to continue tracking them with such accuracy. It is our sincere hope, however, that this report can temporarily increase the costs of Unit 61398s operations and impede their progress in a meaningful way. We are acutely aware of the risk this report poses for us. We expect reprisals from China as well as an onslaught of criticism."
Read more: Mandiant Report Chinese Hacking - Business Insider