The chief of a US agency that is responsible for protecting the US government from cyber attacks has stepped down after a spate of internet-based attacks on government networks.

Randy Vickers stepped down as director of the US Computer Emergency Readiness Team (US-CERT), part of the National Cyber Security Division of the US Department of Homeland Security.

The reason for the resignation has not been disclosed, though the move follows several high-profile hacker attacks lately targeting government websites at the US Senate, Federal Bureau of Investigation, and the Central Intelligence Agency (CIA), including the Gmail accounts of top officials.

Deputy Director Lee Rock, will now serve as acting director until a new director is named.

Formed in September 2003, US-CERT is a partnership between the Department of Homeland Security and the public and private sectors, responsible for the coordination of the response to security threats from the Internet.

CERT is also tasked with reporting information about current security issues, vulnerabilities and exploits through the National Cyber Alert System, and collaborates with software vendors to protect government security networks.