SAN FRANCISCO, US - US federal court officials on Monday 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 emails are crafted with the seal of the US federal court in San Diego, California, and are addressed to executives using their names, addresses and other individual details.

Clicking on a link to see a "subpoena" displays a realistic looking document and stealthily installs malicious computer code in the reader's computer.

"When the recipient tries to view the document, they unwittingly download and install software that secretly records keystrokes and sends the data to a remote computer over the Internet," court officials said in their warning.

"This enables criminals to capture passwords and other personal or financial information and starts software that allows the computer to be controlled remotely."

Subpoenas in the United States are usually served in person to assure judges that the orders from courts have been properly received by those named. --AFP