The actor responsible for cyberattacks against state and local election systems remains unknown to federal officials, Homeland Security Secretary Jeh Johnson said Wednesday, distinguishing the issue from breaches of the Democratic National Committee and related entities.

“It is the case that we face in this country an increasing level of sophistication in terms of cybersecurity attacks from a range of actors, nation-states, criminals, hacktivists,” Johnson said at a forum hosted by The Atlantic.