The head of the organization responsible for defending US government networks against cyberattacks has resigned suddenly and without any explanation.

Randy Vickers, director of the US Computer Emergency Response Team (US-CERT), had been in the post for two years after promotion from deputy director. He will now be replaced by the current deputy director, Lee Rock, until a permanent replacement is named.

US-CERT forms part of the Department of Homeland Security, and deals with attacks on federal government computers and networks, as well as secure private networks regarded as part of the country's critical infrastructure, such as power plants, electric grids and transportation networks.

It's not hard to surmise that Vickers' resignation may have been prompted by the recent string of cyberattacks on US government networks by hacking organizations such as Anonymous and LulzSec. These have included attacks on the CIA, the US Senate and the Oak Ridge National Laboratory, as well as government contractors such as Lockheed Martin.

A House Energy and Commerce oversight subcommittee will today examine government efforts to protect critical infrastructure, and look at the DHS's role faces to protect infrastructure.