A New Corp hack has compromised details of journalists in the US and UK. 

News Corp's US branch says a breach was discovered in late January, affecting the emails and documents of employees, but it claims cybersecurity firm Mandiant was able to contain the breach.

Company executives told employees in a letter seen by reporters;  “We believe the activity affected a limited number of business email accounts and documents from News Corp headquarters, News Technology Services, Dow Jones, News UK, and New York Post”.

“Our preliminary analysis indicates that foreign government involvement may be associated with this activity, and that some data was taken,” executives said.

News Corp Australia was not affected by the hack, the company says.

David Wong, vice-president of consulting at Mandiant, said there are signs that the hackers have “a China nexus, and we believe they are likely involved in espionage activities to collect intelligence to benefit China's interests”.

It is worth noting that attributing the source of a cyber attack or cybercrime is extremely complicated and difficult, both because there is no physical act to observe and because attackers use digital tools to extensively cover their tracks.