A coordinated cyber attack from China targeted at least 48 chemical and defence companies, Symantec has said.
A new report by the security firm has revealed that computers belonging to these companies were infected with malicious software known as "PoisonIvy," which was used to steal information such as design documents, formulas and details on manufacturing processes.
The companies were not identified but Symantec said they include multiple Fortune 100 corporations that develop compounds and advanced materials, along with businesses that help manufacture infrastructure for these industries.
"The purpose of the attacks appears to be industrial espionage, collecting intellectual property for competitive advantage," Symantec said in a white paper on the campaign, which the company dubbed the "Nitro" attacks.
The bulk of the infected machines were found in the United States, Bangladesh and United Kingdom, Symantec said, adding that the victims include 29 chemicals companies, of which some developed advanced materials used in military vehicles.
The cyber campaign ran from late July through mid-September and was traced to a computer system in the United States that was owned by a man in his 20s in Hebei province in northern China, according to Symantec.
Researchers gave the man the pseudonym "Covert Grove" based on a literal translation of his name.
They found evidence that the "command and control" servers used to control and mine data in this campaign were also used in attacks on human-rights groups from late April to early May, and in attacks on the motor industry in late May, Symantec said.
"We are unable to determine if Covert Grove is the sole attacker or if he has a direct or only indirect role," said Symantec's white paper.
"Nor are we able to definitively determine if he is hacking these targets on behalf of another party or multiple parties."
The Nitro campaign is the latest in a series of highly targeted cyber attacks that security experts say are likely the work of government-backed hackers.
Intel's security unit McAfee in August identified "Operation Shady RAT," a five-year coordinated campaign on the networks of 72 organisations, including the United Nations, governments and corporations.
McAfee warned in February that hackers working in China broke into the computer systems of five multinational oil and natural gas companies to steal bidding plans and other critical proprietary information.
Symantec said on Monday that the Nitro attackers sent emails with tainted attachments to between 100 and 500 employees at a company, claiming to be from established business partners or to contain bogus security updates.
When an unsuspecting recipient opens the attachment, it installs "PoisonIvy," a Remote Access Trojan (RAT) that can take control of a machine and that is easily available over the Internet.
While the hackers' behaviour differed slightly in each case, they typically identified desired intellectual property, copied it and uploaded it to a remote server, Symantec said in its report.
Symantec did not identify the companies that were targeted in its white paper and researchers could not immediately be reached. Dow Chemical was not immediately available to comment.
A spokesman for DuPont declined comment, saying: "We don't comment on cyber security issues."