Unintentional interference from radio and space can cause problems for GPS systems, as can deliberate interference and signal spoofing. However, communication companies are unwilling to protect GPS systems from these threats. This is based on the 2012 Homeland Security Report recently released by EE Publishing under the Freedom of Information Act.
The report said: "When GPS jammer hinders communication time allocation or uses GPS time signals as communication resources and affects the normal functions of communication-related critical infrastructure, GPS-based applications may degrade."
Intentional GPS interruption is not a new problem and will not consume too much signal power from the jammer. According to Paul Benshoof of the US Air Force's 746th Test Squadron, only one Piva is required on the GPS antenna to write civilian GPS systems and potential vulnerabilities in an unclassified PowerPoint (PPT).