The U.S. Department of Homeland Security and Federal Bureau of Investigation this week privately warned American businesses about a hacking campaign targeting the nuclear, energy and manufacturing sectors, according to a report by the agencies.
Hackers used tainted "phishing" emails to "harvest credentials" so they could gain access to networks of their targets, the joint analysis report seen by Reuters late on Friday said.
The report said that in some cases hackers succeeded in compromising the networks of their targets, though it did not identify specific victims.
Homeland Security and FBI officials could not immediately be reached for comment on the report, which was dated June 28.
(Reporting by Jim Finkle in Toronto; editing by Grant McCool)