A panel of top cybersecurity officials was briefly left speechless at a congressional hearing Tuesday when Sen. Ted Cruz asked why China had not been sanctioned over a brazen cyber attack on Microsoft Exchange email server software and other attacks. The officials, from Justice Department, the Cybersecurity and Infrastructure Security Agency, and the FBI, were testifying at a Judiciary Committee hearing titled 'America Under Siege: Preventing and Responding to Ransomware Attacks.' Much of the conversation centered on Russia, which the U.S. says at a minimum harbors those who have conducted spectacular ransomware attacks. But Cruz, a Texas Republican, pressed officials...