Kyivstar Cyberattack — Ukraine's Largest Mobile Operator

On December 12, 2023, Kyivstar, Ukraine’s largest mobile operator with over 24 million subscribers, suffered a devastating cyberattack attributed to the Russian state-sponsored group Sandworm. The attack destroyed core network components, causing a near-total collapse of Kyivstar’s mobile and home Internet services.

The outage had immediate cascading effects beyond connectivity: automated air raid alert systems that relied on the Kyivstar network went silent in several regions, forcing cities to use alternative warning methods. Bank ATMs and POS terminals that depended on Kyivstar SIMs stopped functioning, and some critical infrastructure monitoring systems were disrupted.

Kyivstar’s CEO Oleksandr Komarov stated that the attackers had been present in the network since at least May 2023, spending months preparing before triggering the destructive payload. Full service restoration took several days. Ukrainian intelligence linked the intrusion to Sandworm, the GRU-affiliated group responsible for numerous previous attacks on Ukrainian infrastructure.