Outgoing United States Homeland Security Secretary Janet Napolitano today warned of a “major cyber event” in the future that would have a “serious” impact on American society.

In what she described as “a kind of open letter to my successor,” Napolitano warned of terrorist threats, major weather events as a result of climate change and the need to strengthen united states border security.

“Our country will, for example, at some point, face a major cyber event that will have a serious effect on our lives, our economy, and the everyday functioning of our society,” she said.

Napolitano, who resigned in July and will leave office next month after more than four years as the head of the Department of Homeland Security, the administration has yet to name a successor.

The department which was created after the September 2001 attacks plays a key role, in preventing terror attacks, border security and also responding to natural disasters.