Chinese hackers have launched a wave of attacks on mainly U.S. engineering and defense companies linked to the disputed South China Sea, the cybersecurity firm FireEye Inc. said.

The suspected Chinese cyber-espionage group dubbed "TEMP.Periscope" appeared to be seeking information that would benefit the Chinese government, said FireEye, a U.S.-based provider network protection systems. The hackers have focused on U.S. maritime entities that were either linked to — or have clients operating in — the South China Sea, said Fred Plan, senior analyst at FireEye in Los Angeles.

"They are going after data that can be used strategically, so it is line with state espionage," said Plan, whose firm has tracked the group since 2013. "A private entity probably wouldn't benefit from the sort of data that is being stolen."