Story highlights The firm says the hackers were likely gathering intelligence, not trying to disrupt a system

South Korea confirmed Chinese hackers attempted to infiltrate their systems

China is strongly opposed to THAAD's deployment

Hong Kong (CNN) A cybersecurity firm in the United States believes state-sponsored Chinese hackers were trying to infiltrate an organization with connections to a US-built missile system in South Korea that Beijing firmly opposes.

"China uses cyber espionage pretty regularly when Chinese interests are at stake to better understand facts on the ground," John Hultquist, the director of cyber espionage analysis at FireEye, told CNN's News Stream.

"We have evidence that they targeted at least one party that has been associated with the missile placements."

A spokesperson with South Korea's Ministry of Foreign Affairs told CNN there was an attempted cyber attack last month on their systems originating from China, but would not comment when asked if THAAD was targeted.

The official said "prompt defensive measures" blocked the hackers.

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