Russian hacker group Solntsepek claims responsibility for attack on Kyivstar

This is stated in the hackers' message.

"We, the hackers of Solntsepek, take full responsibility for the cyberattack on Kyivstar. We have destroyed 10,000 computers, more than 4,000 servers, all cloud storage and backup systems," the statement says. 

It is noted that they carried out the attack because the company provides communications to the Ukrainian Armed Forces, as well as government agencies and law enforcement agencies of Ukraine.

"The rest of the offices that help the Armed Forces, get ready!" the hackers added.

Instead, the Ukrainian Security Service (SBU) said it was helping Kyivstar restore its network.

"One of the Russian pseudo-hacker groups has already claimed responsibility for the attack. It is a hacker unit of the Main Directorate of the Russian General Staff (better known as the GRU), which thus publicly legalizes the results of its criminal activities," the statement says. 

According to preliminary estimates provided by the SBU, it is planned to restore fixed-line internet for households on December 13, as well as launch mobile communications and the internet.

• On the morning of December 12, Kyivstar users lost mobile service due to a failure: the company says the failure was caused by a powerful hacker attack. The SBU opened criminal proceedings under eight articles, including high treason and sabotage.