Chinabased hackers breached the email account of US Ambassador to China Nicholas Burns as part of a recent targeted intelligencegathering campaign three US officials familiar with the matter told CNN. The hackers also accessed theEmail account of Daniel Kritenbrink the assistant secretary of State for East Asia who recently traveled with Secretary of State Antony Blinken to China. The news first reported by the Wall Street Journal adds to the fallout for the US of the alleged Chinese hack first revealed last week. US officials have consistently labeled China as the most advanced of US adversaries in cyberspace a domain that has repeatedly been a source of bilateral tension in recent years. The FBI has said Beijing has a larger hacking program than all other governments combined. The hacking began in midMay when the Chinabased. hackers used a stolen signin key to burrow their way into email accounts according to Microsoft. A State Department analyst in midJune noticed unusual cyber activity on the departments computer systems and alerted Microsoft to the issue according to multiple sources. Senior cyber officials at the State Department and the US Cybersecurity and Infrastructure Security Agency CISA raced to figure out how serious the breach was. We dont know exactly whats going on but we know theres a problem one US official told summarizing how the State Dept sounded the alarm to other agencies. But a senior National Security Agency official described the activity as standard espionage. That is a fairly traditional threat it is China doing espionage Rob Joyce the NSAs director of cybersecurity said Thursday at the Aspen Security Forum. But Joyce has called another alleged Chinese hacking campaign against maritime and transportation networks and theUS territory of Guam unacceptable because the hackers might use that access to disrupt services in the event of conflict between China and Taiwan. The Chinese foreign ministry accused Washington of conducting its own hacking operations. Last week when Blinken was asked about the hack he would not say how the United States intends to respond. I cant discuss details of our response. Beyond that and most critically this incident remains under investigation Blinken said at a news conference in Jakarta Indonesia. But that is something that happens. The fact that US officials and Microsoft analysts initially had trouble identifying how the hackers got into the email accounts told US officials they were dealing with a sophisticated hacking team the other US official said. The State Department raised the issue of the hacking incident in a meeting with top Chinese diplomat Wang Yi last week a senior State Department official says. A senior CISA official told he fielded calls about the breach while on a weekend getaway out of Washington with his children. The critical work that the State. Department does conduct on behalf of the American people made it important to understand howserious the hack was. The U.S. officials generally operate with the assumption that anything on the unclassified network can be hacked. Still the Biden administration believes that the Chinese hacking operation gave Beijing insights about US thinking heading into Blinken’s highstakes trip to China in June has reported. But the hackers had a month head start on US government responders.