According to foreign media reports on Engadget website, the U.S. government is no stranger to ordinary network attacks, but recently in dealing with the government's e-mail system, it has made an extreme approach, that is, to shut down the e-mail system to prevent hackers.
Last weekend, the U.S. State Department shut down the entire unclassified e-mail system to strengthen network defense, because at the same time earlier, hackers invaded the White House through the e-mail system. And guess these attacks come from China and Russia, which means that Chinese hackers can not be prevented.