It was reported on May 15, 2015, that Penn State University President Eric Barron wrote to 500 partners, comprising companies, government agencies, and other universities as well as 18,000 students and professors whose personal data, including social security numbers, were on one of the computers, of "the advanced attack against our College of Engineering by very sophisticated threat actors.” Among Penn State’s specialties is aerospace engineering, which has both commercial and defense applications important to China’s government. The university is also home to Penn State’s Applied Research Laboratory, one of 14 research centers around the country that work mainly for the military. University sources say that the lab’s computers are separated from the engineering college by “network-based controls”. The University's Applied Research Lab has been doing work for the Navy since 1945 and specializes in undersea propulsion and navigation, offering a potential treasure trove of technology that’s already being developed with partners for commercial applications. The Federal Bureau of Investigation (FBI) notified the University of the breach in November 2014, triggering a months-long investigation that eventually found two separate groups of hackers stealing data. One group has been linked by investigators to the Chinese government while the second has not yet been identified, though investigators believe it is the work of state-sponsored hackers.