# AIS Data Vulnerability Indicated by a Spoofing Case-Study
## 3 Results
### AIS Vulneribilities  
To date, some studies have been conducted on the vulnerabilities of AIS. [PERSON] et al. [27] discussed the security evaluation of AIS and divided the AIS threats into three macro-categories: spoofing, hijacking, and availability disruption, based on software or radio frequency (RF) threats. [PERSON] pointed out that the vulnerability of the AIS VHF broadcast frequency can lead to bandwidth usurpation by potential attackers who can prevent other devices from transmitting, negatively affect the synchronization process, or change slot reservation/assignment information [28]. [PERSON] and [PERSON] [16], as well as [PERSON] et al. [9], emphasized that AIS-broadcasted messages are neither encrypted nor authenticated, making them vulnerable to unauthorized manipulations. The vulnerabilities of the AIS arise mainly from its technical performance. The AIS is an open-source system that transmits on VHF channels in the maritime mobile band [1; 3]. The data sent by the transponders are simply not subject to any control or verification of their integrity [16; 29]. Data exchange between stations in the AIS service is largely based on transmission and reception at RF, and therefore the AIS service is vulnerable to malicious transmissions and risks of data manipulation [1]. Figure 3 shows the concept of AIS service and possible vulnerabilities in the form of spoofing via RF. At the center of the AIS service are base stations designed for use by government agencies to manage the VDL to provide wide Vessel Traffic System (VTS) or Coastal Surveillance coverage [1]. Base stations are vulnerable to possible attack if someone sends false AIS signals that can overload time slots and prevent or complicate the operation of regular AIS stations. AIS SAR devices are MOB-AIS, EPIRB-AIS, and AIS SART stations. These stations use a radio beacon system and are designed to transmit distress signals with geographic coordinates, allowing SAR units to more accurately locate survivors [27]. In addition to this advantage, if the attackers generate false distress signals, this could lead to the deception of shipborne AIS stations, VTS SAR services, and facilities. AtoN is also part of the AIS service that could enhance the safety of navigation, especially in coastal navigation (i.e., shallow waters, port approaches, navigational obstacles) with high traffic density. It should be emphasized that not all ships are equipped with AIS and ECDIS [30]. From an operational point of view, AIS AtoNs are identified as physical, synthetic and virtual [1]. Based on the technical characteristics, it is obvious that synthetic and virtual AtoNs (V-AtoN) are more vulnerable to spoofing than physical AtoNs. The V-AtoN can easily be spoofed intentionally [31]. Spoofed AtoN signals can mislead the OOW during navigation. Combining virtual and physical AtoNs is considered an effective measure to avoid the negative consequences of V-AtoN spoofing [32]. The possibility of V-AtoN spoofing should be considered as the main vulnerability due to the dependence of AIS on GNSS, which is also vulnerable to spoofing [30; 33]. Ship-borne Class A and B as the main component of the AIS service could enhance MSA and collision avoidance. AIS vulnerabilities can result in different errors and falsifications of messages, which may have, in some cases, a significant impact on mariners and local authorities MSA. In case of a malicious attack, a false maritime picture could occur  
Figure 3: AIS mobile and fixed station RF-based spoofing, according to the authors of [3; 6; 27]. and mislead the OOW in navigation or VTS. These may affect decision-making processes in navigation and surveillance. [PERSON] et.al. [34] presented a risk analysis of the AIS supported by the EBIOS (fra. Expression des Besoins et Identification des Objectifs de Securite) methodology and an anomaly typology. The EBIOS method is used in risk evaluation and contributes to the security assessment of the AIS system.