  Wireless sensor networks have emerged as an important and new area in
wireless and mobile computing research because of their numerous potential
applications that range from indoor deployment scenarios in home and office to
outdoor deployment in adversary's territory in tactical battleground. Since in
many WSN applications, lives and livelihoods may depend on the timeliness and
correctness of sensor data obtained from dispersed sensor nodes, these networks
must be secured to prevent any possible attacks that may be launched on them.
Security is, therefore, an important issue in WSNs. However, this issue becomes
even more critical in cognitive wireless sensor networks, a type of WSN in
which the sensor nodes have the capabilities of changing their transmission and
reception parameters according to the radio environment under which they
operate in order to achieve reliable and efficient communication and optimum
utilization of the network resources. This survey paper presents a
comprehensive discussion on various security issues in CWSNs by identifying
numerous security threats in these networks and defense mechanisms to counter
these vulnerabilities. Various types of attacks on CWSNs are categorized under
different classes based on their natures and tragets, and corresponding to each
attack class, appropriate security mechanisms are presented. The paper also
identifies some open problems in this emerging area of wireless networking.
