Detecting and removing spoofing signals

The method 100 and device comprises a way to receive a radio frequency signal 102, from a navigation or communications devices; performing anti-spoofing assessment, detecting the presence of a spoofed signal 108; generate a replica of the spoofing signal 106; subtract the replica from the RF signal 114 to provide a residual non-spoofed signal and decode said residual signal 116. Performing the anti-spoofing assessment may comprise comparing a measured and predicted angle of arrival and determining that the signal is spoofed if they are not equal. The predicted angle may be from a predicted location of source, or ephemeris data. The spoofing signal may include a navigation code from a particular navigation satellite. The removal may be performed by an iterative process, until a cross-correlation of a lagged frequency shifted coarse acquisition pseudorandom noise code C/A PRN is reduced to correlation noise. The RF signals may be from GPS satellites and have attributes such as C/A PRN sequences, a modulation for C/A PRN, a time lag a Doppler shift. These attributes can be used to generate a cancellation waveform for the spoofing signal by the use of the iterative process.