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GNSS is nowadays used as a primarily timing source for the synchronization of various types of networks and has been defined as the backbone of the connected world and the invisible utility to highlight its pervasive presence in digital infrastructures. Despite this growing dependency on GNSS, network operators rarely perceive the vulnerability of GNSS receivers to interference or jamming as a real problem. The awareness about GNSS spoofing, namely the transmission of false signals with the intent to fool receivers, is low, while in most cases users and stakeholders continue to consider GNSS a non-critical commodity. A stationary GNSS receiver used for timing and synchronization is an ideal target for malevolent attacks because the antenna is static and often sited in a visible location. As an addition to advanced signal processing and use of backup technologies, the proposition of authenticated GNSS signals is seen as a powerful way to increase the resilience of satellite-based time synchronization. Recognizing this fact, the European Galileo program is gradually implementing the OSNMA authentication service, with a test signal already available from some satellites. Today most of the GNSS-based time synchronization systems on the market are built upon low-cost GPS-only, single-frequency modules, which provide PPS accuracy in the range 20 to 100 ns. Under open sky conditions, those modules do provide a stable time reference, but are very sensitive to degradations. With no doubts, the majority of timing receivers are relatively easy to jam and spoof given the low signal level handled at the antenna. Those degradations range from an increase of the PPS jitter due to a reduced number of satellites in view, to a complete loss of the PPS synchronization in the case of jamming of the single GPS L1 C/A signal. Septentrio is introducing the high-end mosaic-T module, a highly secure, resilient, and accurate GNSS timing module for critical infrastructure and mission-critical timing applications. The use of high-end GNSS receiver as source for synchronization first allows decreasing the noise/jitter on the PPS signal thanks to the use of more satellites and signals in the time solution. The multi-frequency multi-constellation positioning also brings an immediate increase of resilience and robustness in case of unintentional interference knocking out a band or a constellation. On top of its AIM+ interference monitoring and mitigation technology, Septentrio is deploying Galileo’s OSNMA support on its product portfolio and network timing synchronisation was identified as critical market for an increased robustness to jamming/spoofing attacks. The presentation reports on jamming and spoofing tests performed in the framework of the ROOT project. We start by a risk assessment of different interference/jamming/spoofing scenarios for network timing synchronization. We will prioritize the different GNSS threats for this industry, with a special attention on the added value of Galileo OSNMA, which is expected to set a new standard on the industry. We then present different test scenarios selected to measure the actual resilience of the receiver. Initial results from this test campaign are already presented, showing the benefit of OSNMA for time synchronisation of networks. Acknowledgment: This work was developed within the ROOT project (www.gnss-root.eu) funded by the European GNSS Agency under the European Union’s Horizon 2020–G.A. n. 101004261.