  In this paper we investigate the problem of designing a spectrum scanning
strategy to detect an intelligent Invader who wants to utilize spectrum
undetected for his/her unapproved purposes. To deal with this problem we apply
game-theoretical tools. We model the situation as a game between a Scanner and
an Invader where the Invader faces a dilemma: the more bandwidth the Invader
attempts to use leads to a larger payoff if he is not detected, but at the same
time also increases the probability of being detected and thus fined.
Similarly, the Scanner faces a dilemma: the wider the bandwidth scanned, the
higher the probability of detecting the Invader, but at the expense of
increasing the cost of building the scanning system. The equilibrium strategies
are found explicitly and reveal interesting properties. In particular, we have
found a discontinuous dependence of the equilibrium strategies on the network
parameters, fine and the type of the Invader's award. This discontinuity on
fine means that the network provider has to take into account a human factor
since some threshold values of fine could be very sensible for the Invader,
while in other situations simply increasing the fine has minimal deterrence
impact. Also we show how different reward types for the Invader (e.g. motivated
by using different type of application, say, video-streaming or downloading
files) can be incorporated into scanning strategy to increase its efficiency.
