Hackers working in China broke into the computer systems of five multinational oil and gas companies to steal bidding plans and other critical proprietary information, the computer security firm McAfee Inc said in a report.

The report, which named the attacks Night Dragon, declined to identify the five known companies that had been hacked and said that another seven or so had also been broken into but could not be identified.

“It … speaks to quite a sad state of our critical infrastructure security. These were not sophisticated attacks … yet they were very successful in achieving their goals,” said Dmitri Alperovitch, McAfee's vice president for threat research.

The hackers got into the computers in one of two ways, either through their public websites or through infected emails sent to company executives.

During the at least two years — and up to four years — the hackers had access to the computer networks, they focused on financial documents related to oil and gas field exploration and bidding contracts, said Alperovitch.

They also copied proprietary industrial processes.

Read the complete Reuter's story, “Chinese hackers infiltrated five energy firms: McAfee.”