Kyiv, Dec 13 (Reuters) – Kyivstar, Ukraine's leading mobile phone operator, has begun the process of restoring voice services to select clients following a significant cyber attack, according to Kyivstar CEO Oleksandr Komarov. The attack, which occurred on Tuesday, inflicted substantial damage, disrupting services for more than half of Ukraine's population. Komarov described it as "the biggest cyber attack on telco infrastructure in the world."

While voice services are being gradually reinstated, data and other services are expected to follow suit. The company's CEO emphasized the severity of the situation, attributing the attack to a well-planned, long-term assault on Ukrainian critical infrastructure.

Kyivstar, serving approximately 24 million private consumers, offers mobile, internet, and various other services, playing a crucial role in supporting private businesses and digitized state services.

In response to the attack, which two Russian groups have claimed responsibility for, a massive effort involving hundreds of experts and institutions is underway to restore services. Komarov stated that the restoration process would be implemented step by step to ensure stability and resilience against potential loads.

The cyber attack is part of a broader pattern, with Russia targeting Ukraine's critical infrastructure since the invasion in February 2022. Hundreds of missiles and drones have frequently targeted power, grain, and port facilities.

Komarov revealed that Kyivstar has faced numerous cyber attacks since the start of the war, ranging from distributed denial of service (DDoS) attacks to attempts to breach networks and use infrastructure in occupied territories. Despite the challenges, the company remains committed to restoring services.

Ukraine's SBU security service is investigating the attack, and Kyivstar is actively collaborating with the authorities. While daily revenue has been affected, Kyivstar's parent company, Veon, reassured that voice services were being restored, rejecting social media suggestions of compromised customer data.

The gradual restoration process indicates a strategic and careful approach to ensure the stability and security of services for Kyivstar's extensive user base.