The Alamitos natural gas-fired power station is seen on Oct. 1, 2009 in Long Beach, Calif. / Photo by David McNew/Getty Images
The Department of Homeland Security acknowledged Wednesday that it has been working with infrastructure owners to combat a "series of cyber intrusions targeting natural gas pipeline companies."
The intrusions involve "spear-phishing," a type of targeted email fraud used to trick personnel within the natural gas companies, DHS said in a statement. The emails appear to come from a trusted source, but can be used to steal passwords or install malicious software on the recipient's computer if they click on links or attachments.
ABC News first reported on the recent attacks, originating from an "unidentified group of hackers." U.S. officials who spoke to ABC said it was unclear whether a foreign power, such as China, or someone else was behind the attacks.
DHS is working with the FBI to identify the perpetrators.