US federal court officials have warned that hackers are emailing phony subpoenas embedded with malicious software to high-ranking executives to steal valuable corporate information.

Thousands of powerful US executives have received the bogus emails that contain links which, if clicked on, install software letting hackers take control of computers and swipe passwords or other sensitive data.

Internet security insiders refer to the attacks as “whaling” because they use social-engineering trickery involved in “phishing” but target individual “big phish” instead of casting nets in a sea of Internet users.

“The success rate was incredibly high,” Websense Security Labs manager Stephan Chenette told AFP.

“Most likely due to the nature of the content and the real data, the emails had their exact names and legal language in there that made it seem like a serious subpoena.”