TRANSACTIONS ON MARITIME SCIENCE 361 Trans. marit. sci. 2021; 02: 361-373 University of Ljubljana, Faculty of Maritime Studies and Transport, Portorož, Slovenia e-mail: andrej.androjna@fpp.uni-lj.si The development of contemporary navigation and positioning systems have signifcantly improved reliability and speeds in maritime navigation. At the same time, the vulnerabilities of these systems to cyber threats represent a remarkable issue to the safety of navigation. Therefore, the maritime community has raised the question of cybersecurity of navigation systems in recent years. This paper aims to analyse the vulnerabilities of the Global Navigation Satellite System (GNSS), Electronic Chart Display Information System (ECDIS) and Automatic Identifcation System (AIS). The concepts of these systems were developed at a time when cybersecurity issues have not been among the top priorities. Open broadcasts, the absence of or limited existence of data encryption and authentication can be considered as their primary security weaknesses. Therefore, these systems are vulnerable to cyber-attacks. The GPS as the data source of a ship’s position can relatively easily be jammed and/or spoofed, increasing the vulnerabilities of ECDIS and AIS. A systematic literature review was conducted for this article, supplemented Impact of Spoofing of Navigation Systems on Maritime Situational Awareness Andrej Androjna, Marko Perkovič KEY WORDS ~ Cybersecurity ~ Jamming ~ Spoofng ~ Safety of navigation ~ Shipboard navigation systems 1. INTRODUCTION Maritime cybersecurity represents one of the most important segments of maritime security policy in general. Today’s maritime industry is highly dependent on digitalisation. Modern digital systems are used in many segments of the maritime sector, including port authorities, national maritime administrations, maritime trafc management systems, shipping companies, and vessel monitoring and management systems. The trend towards digitisation and integration of systems is largely present in the maritime sector. Most of the ship navigation, communication and control systems are integrated and use the Internet for successful operation (Middleton, 2014; Chybowski et al., 2019; Dobryakova et al., 2018). Modern information technologies, together with digitalisation and integration trends, have signifcantly accelerated and improved the processes of management, safety and control in the maritime sector. However, it is important to emphasise that these technologies are vulnerable to cyber-attacks. The number of these attacks shows a trend of signifcant growth. Cyber-attacks in the maritime industry have increased by 900% between 2017 and 2019 (Marine Insight, 2020). As the International Maritime Organization (IMO) gives great importance to maritime security issues, it has adopted resolution MSC.428 (98) “Marine Cyber Risk Management in This work is licensed under doi: 10.7225/toms.v10.n02.w08 by a SWOT analysis of the AIS service and particular case studies of recent cyber-attacks on these systems. The analysis of selected case studies confrmed that these systems could easily be spoofed and become a subject of data manipulation with signifcant consequences for the safety of navigation. The paper provides conclusions and recommendations highlighting the necessity for the users to be aware of the vulnerabilities of modern navigation systems. Received on: 11.06.2021; Revised on: 14.08.2021; Accepted on: 22.08.2021; Published online: 23.09.2021