By Raphael Satter and AJ Vicens WASHINGTON (Reuters) -Chinese state-sponsored hackers breached the U.S. Treasury Department's computer security guardrails this month and stole documents in what Treasury called a "major incident,

The Treasury Department was breached by a China-sponsored actor earlier this month, officials told Congress in a letter on Monday. The "major" breach was achieved by gaining access to a third-party cybersecurity service Treasury used,