The security and resilience of the electricity system are critical for TSO and DSO work plans because they directly impact the reliability and stability of the power supply. As the energy system becomes more decentralised and integrates higher shares of renewable and digital technologies, new challenges emerge, such as increased hybrid threats, variability in generation, and the need for real-time coordination. Incorporating security and resilience into the TSO–DSO work plan ensures that both operators can proactively manage risks, maintain grid reliability, and support the broader goals of the energy transition.