The 2G/3G sunset is the planned retirement of older mobile networks so operators can reclaim radio spectrum, cut operating costs, and focus on newer systems such as LTE and 5G. It does not just remove old antennas; it also removes legacy signaling, authentication, and voice paths that many older devices and services still depend on.
In cybersecurity, the sunset matters because old networks often carry weaker security assumptions and create transition risks. Attackers may exploit leftover 2G or 3G support for downgrade attacks, interception, device tracking, or abuse of aging infrastructure that has not been maintained well. Defenders use the sunset to reduce attack surface, but they must manage the migration carefully: verify emergency calling, SMS, roaming, and authentication behavior; isolate legacy interconnects; and disable fallback where it is no longer needed. The main risk is not the retirement itself, but the gaps left behind when modern and legacy systems overlap.