1. Introduction
2. Security and Privacy Issues in WSNs
   2.1 Denial of Service (DoS) Attacks
3. Security Mechanisms in Traditional WSNs
4. Security Vulnerabilities in CWSNs
   4.1 Attacks on the communication protocols
   4.2 Masquerading attacks
   4.3 Unauthorized access of spectrum
   4.4 Physical attacks on the sensor nodes
   4.5 Internal failure of the sensor nodes
   4.6 Power exhaustion attack on the sensor nodes
   4.7 Attacks on objective functions of cognitive engine
   4.8 Attacks on the security policies of the sensor nodes
   4.9 Attacks on the cryptographic protocols
   4.10 Attacks on the privacy of sensor data
5. Work on Identification of CWSN Threats
6. Security Mechanisms for CWSNs
7. Emerging Research Directions
8. Conclusion