Nakasone did not provide any details of the operations but claimed that they were lawful, conducted under civilian oversight and guided by Defense Department policy.
"We’ve conducted a series of operations across the full spectrum; offensive, defensive, [and] information operations," the report cited Nakasone as saying.
The United States also has conducted so-called "hunt forward" operations related to the alleged risk of Russian cyber-attack, the report said. The operations have allowed the United States to chase down foreign hackers as well as identify their tools before they could be used against the United States, the report added.
"We remain vigilant every single day. Every single day. I think about it all the time," Nakasone said regarding concerns about potential Russian cyber-attacks against the United States.
Earlier in May, Russian Ambassador to the United Nations Vasily Nebenzia said the US government had offered $10 million to persons who will provide "evidence" of Russian intelligence services' alleged involvement in cyber-attacks against the United States. Nebenzia pointed out it is United States and other Western governments that are deliberately leveraging hacker networks in cyber-attacks.