function attack (OFA) [8]. This attack mainly targets thelearning engine of cognitive radios. In cognitive radios, a cognitive
engine has the ability to tune many parameters to maximizeits objective function. These objective functions take as
variables high transmission data rate, low power consumption,low delay, and high security level. Such parameters might
include bandwidth, power, modulation type, coding methods,MAC protocol, routing schemes, and encryption mechanisms
Among those variables of the objective function, hightransmission rate and low delay are related to the channel,
while low power consumption and high security level are directly determined by the inputs of the users. So for an objective
function attack, whenever the user wants to raise the security level, the malicious nodes may use some ways to increase
the delay of the user. Thus, the user may connect high delay with high security level and not want to use high security level
at all. Thus, it will become more susceptible to security attacks.It is necessary to remark that the OFA performance is related
to which optimization method is used in the cognitive radio network Some cognitive radios perform optimization instantly after getting the input of the environment. On the other hand, other cognitive radios observe the environment
just once, then search for an optimized result, and the decision will not be changed by the input of the environment. In this
case, the type of cognitive radio is not affected by OFAs. However,cognitive radio devices generally have high sensing ability and perform optimization frequently. Therefore, a cognitive radio network is susceptible to OFA attacks.