The ASX-listed company is the only non-Chinese significant producer of separated rare earths, used for a variety of purposes including military equipment.
It was earlier this month awarded a $US120 million ($A174m) contract by the US Department of Defence to build a processing facility in Texas.
A report by cybersecurity firm Mandiant on Wednesday said a pro-Chinese campaign known as Dragonbridge appeared to be targeting Lynas, as well as other rare earths companies in Canada and the US.
It identified "inauthentic social media and forum accounts, including those posing as residents in Texas to feign concern over environmental and health issues surrounding the plant".
The accounts claimed the plant would expose residents to radioactive contamination, cancer risks and deformities in newborns.
Lynas plans to relocate aspects of its processing operations to a new plant being developed in Western Australia's Goldfields.
It has faced controversy over low-level radioactive waste generated by its existing plant in Malaysia.
In a statement, Lynas said it had been the subject of "disinformation campaigns".
"The report shows evidence of direct and mutual engagement between the pro-China Dragonbridge social media accounts and the Malaysian anti-Lynas activists," it said.
"Lynas is proud of our record as an ethical and environmentally responsible rare earths producer and as a lawful and compliant company."
Experts believe the campaign is designed to denigrate potential threats to China's global market dominance in rare earths mining.
"The private sector is now the victim of attacks by Chinese information operations which is growing increasingly aggressive," Mandiant's John Hultquist said.
"An economic decoupling with China will only encourage more victimisation of the private sector by Chinese actors. Unfortunately businesses will be on the front lines of a fight that may not be fair."
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