  Command, Control, Communication, and Intelligence (C3I) system is a kind of
system-of-system that integrates computing machines, sensors, and communication
networks. C3I systems are increasingly used in critical civil and military
operations for achieving information superiority, assurance, and operational
efficacy. C3I systems are no exception to the traditional systems facing
widespread cyber-threats. However, the sensitive nature of the application
domain (e.g., military operations) of C3I systems makes their security a
critical concern. For instance, a cyber-attack on military installations can
have detrimental impacts on national security. Therefore, in this paper, we
review the state-of-the-art on the security of C3I systems. In particular, this
paper aims to identify the security vulnerabilities, attack vectors, and
countermeasures for C3I systems. We used the well-known systematic literature
review method to select and review 77 studies on the security of C3I systems.
Our review enabled us to identify 27 vulnerabilities, 22 attack vectors, and 62
countermeasures for C3I systems. This review has also revealed several areas
for future research and identified key lessons with regards to C3I systems'
security.
