A report from the United States Government Accountability Office indicated that some of the country's most advanced fighter jets face severe security risks which could compromise them in combat. The Automatic Dependent Surveillance-Broadcast (ADS-B) Out transponder technology has been installed on several U.S. military aircraft since 2010, and a rule of the Federal Aviation Administration put in place in 2010 requires all military aircraft to be equipped with ADS-B Out transponders by the beginning of 2020. These systems however carry with them several inherent security risks which have not been addressed by either the Department of Defense or the FAA.The ADS-B Out provide highly detailed information including an aircraft’s registration number, longitude and latitude, dimensions and velocity - invaluable data well beyond what radar detection could ever provide. While older transponders such as the Mode S broadcast aircraft specific International Civil Aviation Organisation code, squawk code and altitude, the details transmitted by newer transponders could leave aircraft extremely vulnerable of compromised by an adversary. If new transponders are compromised aircraft can be tracked far more precisely than radar ever could and invaluable targeting information could be fed to hostile anti aircraft weapons systems such as fighters and air defence complexes. The Government Accountability Office tested their theory regarding the vulnerability of U.S. military aircraft by using commercially available receivers, and succeeded in tracking several types of aircraft. They noted that it was well within the capabilities of potential adversaries to do the same, and to exploit such vulnerabilities to launch cyber attacks against U.S. platforms. The GAO's findings on the vulnerabilities of new transponders were supported by an assessment by the RAND Corporation in 2015 which concluded that broadcasting such detailed unencrypted information posed severe security risks. They noted the F-22 Raptor in particular and the potential for highly classified information on its stealth capabilities to be obtained by hostile adversaries. Ultimately alongside advancing counter stealth technologies, the use of transponders to provide detailed information on the movements of stealth aircraft could well prove to be another invaluable means for U.S. adversaries to target and destroy its most advanced combat aircraft.