Digital intruders broke into News Corp. email accounts and compromised the data of an unspecified number of journalists, the company disclosed Friday. The media firm’s internet security adviser said the hack was likely aimed at gathering intelligence for Beijing’s benefit. News Corp., which publishes the Wall Street Journal, said the breach was discovered in late January and affected emails and documents of what it described as a limited number of employees, including journalists. It said that cybersecurity firm Mandiant had contained the breach. David Wong, vice president of consulting at Mandiant, said the hackers were believed to have “a China...