In the latest escalation of cyber attacks surrounding Crimea, NATO announced Sunday that several of its websites, including its unclassified email network and the NATO-affiliated cyber security center in Estonia, had been hacked. A Ukrainian hacker group that calls itself Cyber Berkut has claimed responsibility for crashing and disrupting services on multiple NATO websites, but the claim has not been independently confirmed. In recent weeks, Cyber Berkut claimed attacks on Russian websites, but its decision to focus on NATO marks a new turn. A statement released by Cyber Berkut said "We will not allow the presence of NATO in our homeland.” Despite the annoyances caused by the attack, a NATO official told Reuters "It doesn't impede our ability to command and control our forces. At no time was there any risk to our classified networks."