A radio frequency receiver system comprising: an antenna configured to receive a radio frequency input signal corresponding to a global navigation satellite system signal with a course acquisition code; a radio frequency signal front-end system configured to process the radio frequency input signal to generate an equivalent digital signal; and a spoof detection system (16, 50) comprising: a memory configured to store a predetermined baseline power spectral density corresponding to a baseline radio frequency signal in which the spoofing signal component is known to be absent; a power spectral density processor (18, 52) configured to generate a time-averaged power spectral density of the equivalent digital signal; and a power spectral density comparator (20, 62) configured to: - filter the time-averaged power spectral density of the equivalent digital signal to remove time averaged samples associated with the course acquisition code; and - implement a statistical difference algorithm across the time-averaged power spectral density of the equivalent digital signal relative to the predetermined baseline power spectral density to detect a spoofing signal component in the radio frequency input signal. an antenna configured to receive a radio frequency input signal corresponding to a global navigation satellite system signal with a course acquisition code; a radio frequency signal front-end system configured to process the radio frequency input signal to generate an equivalent digital signal; and a spoof detection system (16, 50) comprising: a memory configured to store a predetermined baseline power spectral density corresponding to a baseline radio frequency signal in which the spoofing signal component is known to be absent; a power spectral density processor (18, 52) configured to generate a time-averaged power spectral density of the equivalent digital signal; and a power spectral density comparator (20, 62) configured to: - filter the time-averaged power spectral density of the equivalent digital signal to remove time averaged samples associated with the course acquisition code; and - implement a statistical difference algorithm across the time-averaged power spectral density of the equivalent digital signal relative to the predetermined baseline power spectral density to detect a spoofing signal component in the radio frequency input signal. a memory configured to store a predetermined baseline power spectral density corresponding to a baseline radio frequency signal in which the spoofing signal component is known to be absent; a power spectral density processor (18, 52) configured to generate a time-averaged power spectral density of the equivalent digital signal; and a power spectral density comparator (20, 62) configured to: - filter the time-averaged power spectral density of the equivalent digital signal to remove time averaged samples associated with the course acquisition code; and - implement a statistical difference algorithm across the time-averaged power spectral density of the equivalent digital signal relative to the predetermined baseline power spectral density to detect a spoofing signal component in the radio frequency input signal. - filter the time-averaged power spectral density of the equivalent digital signal to remove time averaged samples associated with the course acquisition code; and - implement a statistical difference algorithm across the time-averaged power spectral density of the equivalent digital signal relative to the predetermined baseline power spectral density to detect a spoofing signal component in the radio frequency input signal.