## 3 Materials and Methods
### Threat Modeling Using TV-HARM
#### 3.4.2 Application of TV-HARM in Satellite Networks
This disrupts orbital control and data transmission in _MEO_ and _LEO_ satellites, destabilizing the space segment. The interconnected nature of the space and user segments amplifies the impact, as threats originating in space can reverberate back to the user segment. For example, GNSS services could disseminate inaccurate location data, leading to widespread disruptions in the satellite network. This scenario highlights severe compromises in data integrity and service reliability across the network. Attack Scenario 3 (\(tv_{123\text{-}MEO}\)): The attacker exploits a vulnerability in _MEO_ satellites within the space segment, initiating threats that propagate to the ground and user segments and causing widespread network disruption. The attack begins by leveraging a CCSDS vulnerability in _MEO_ satellites to inject malicious instructions into critical nodes in the ground segment, such as the _GCS_ and \(GW_{2}\). Malicious data transmitted to the _GCS_ exploit host vulnerabilities and use TCP/IP pathways to access \(GW_{1}\) and \(GW_{2}\). Within these gateways, the attacker manipulates data flows, corrupting transmissions to _LEO_ satellites and user segment nodes, such as _ULAVs_, the _IoT_, and the _GNSS_. In particular, commands to the _GNSS_ are compromised via an NMEA vulnerability, resulting in inaccurate location data. These errors cascade through dependent services in the user segment, disrupting operational stability and data integrity. This scenario illustrates how an attack originating from the space segment can cascade into the ground and user segments, destabilizing satellite and terrestrial communications. Attack Scenario 4 (\(tv_{123\_LEO}\)): The attacker exploits a vulnerability in the space segment, specifically targeting _LEO_ satellites, to propagate threats across the ground and user segments, disrupting the satellite network. The attack initiates with malicious data generated in _LEO_ satellites, which are transmitted to the _GCS_ and \(GW_{1}\). As a central node, the _GCS_ becomes a focal point for host vulnerabilities, allowing the manipulation of command structures and data flows. Exploiting TCP/IP vulnerabilities, the attack spreads further to \(GW_{1}\) and \(GW_{2}\), propagating malicious instructions to the user segment. In the user segment, the _UAV_ and the _IoT_ are targeted, leveraging NMEA vulnerabilities to corrupt commands transmitted from \(GW_{2}\) to the _GNSS_. Consequently, inaccurate location data compromise dependent services. The _RT_ facilitates the spread of malicious data from _LEO_ satellites to \(GW_{1}\), causing the initial attack to cascade through the ground segment and affect the user segment. This corruption of the data and command structures, originating in _LEO_ satellites, disrupts communication across all the segments, undermining the reliability and stability of satellite communications and user services. These cascading effects underscore the interdependencies among the ground, space, and user segments, highlighting the importance of comprehensive threat modeling to analyze vulnerabilities and enhance satellite network security. Future work will focus on quantitatively assessing these scenarios to develop effective security measures.