In a raid seeking information related to Israel’s Iron Dome missile defense system, Chinese hackers infiltrated the databases of three Jewish defense contractors.

In addition to taking information on the Iron Dome, the attackers were also able to nab plans regarding other projects – including Unmanned Aerial Vehicles, ballistic rockets, and “detailed schematics and specifications” for the Arrow III missile interceptor.

According to independent journalist Brian Krebs, the intrusion occurred between 2011 and 2012 and was carried out by China’s infamous “Comment Crew” – a group of cyber warriors linked to the Chinese People’s Liberation Army (PLA).

In May, the United States charged five members of this group with cyber espionage against American computer networks. The hackers reportedly infiltrated US systems in order to “steal information that would provide an economic advantage” for Chinese companies, including “Chinese state-owned enterprises.”

Although it’s unclear exactly how much data the hackers were able to obtain, Maryland-based intelligence firm Cyber Engineering Services (Cyber ESI) identified more than 700 documents that were stolen. The real number is believed to be much higher.

Speaking to Business Insider, University of California researcher Jon Lindsay said the intrusion could signal that the Chinese are interested in learning more about missile defense – which is considered notoriously difficult to become proficient in – but it could also be an extension of Beijing’s typical cyber espionage practices.

"The Chinese style of espionage is more like a vacuum cleaner than a closely-directed telescope," Lindsay said. "They go after a lot of different kinds of targets — the leaders in any particular industry."

As the news outlet speculated, Chinese interest in the Iron Dome could have been triggered by the missile shield’s success during Israel’s battle with Hamas in 2012. Krebs noted that Israel claims the Iron Dome has intercepted one-fifth of the 2,000-plus rockets fired their way in the most recent outbreak of violence.

Regarding the hack, one of the Israeli defense firms involved declined to say whether any of its partners in the US were alerted to the security breach, which is notable considering that Congress has delivered hundreds of millions of dollars to Tel Aviv in Iron Dome funding.

“At the time, the issue was treated as required by the applicable rules and procedures,” Eliana Fishler, a spokesperson for the defense firm Israel Aerospace Industries, said to Krebs. “The information was reported to the appropriate authorities. IAI undertook corrective actions in order to prevent such incidents in the future.”

Meanwhile, CyberESI CEO Joseph Drissel explained that much of the stolen information was restricted by the US State Department.

“Most of the technology in the Arrow 3 wasn’t designed by Israel, but by Boeing and other U.S. defense contractors,” he told Krebs. “We transferred this technology to them, and they coughed it all up. In the process, they essentially gave up a bunch of stuff that’s probably being used in our systems as well.”

Of course, the US has accused Beijing of this type of espionage before, even outside of the five Chinese officials charged in May. As RT reported in June, American cyber security company CrowdStrike said that one unit within the PLA has been linked to seven years of hacking against the US aerospace industry. This information was shared with US intelligence agencies as well as the Justice Department.

For its part, China has consistently denied allegations of hacking, often claiming that it is subject to numerous cyber attacks from the United States.