Abstract: Disclosed is a technique that can provide one or more countermeasures against spoofers. An antenna, movable in space, is used to receive space vehicle (SV) signals that appear to be associated with a plurality of space vehicles of a global navigation satellite system (GNSS). SV signals are identified that have similar signal power and/or phase signatures that respectively appear to be associated with at least a first space vehicle and a second space vehicle of the GNSS. An existence of a spoofer is identified based at least in part on the identification of SV signals that have similar signal power and/or phase signatures that respectively appear to be associated with at least the first space vehicle and the second space vehicle of the GNSS.