The US has a new head of cyber security, amid concerns about the Bush administration's commitment to protecting computer networks from attack.
Amit Yoran only gave one day's notice
The post was left vacant by the sudden resignation of Amit Yoran a week ago.
Reports suggested he left because his team was not given enough clout within the Department of Homeland Security.
The new acting head of the National Cyber Security Division is Andy Purdy, the former deputy director.
Mr Purdy has been a member of the organisation since it was set up in September 2003.
The division has a staff of about 60 people and a budget of about $80m (£44.54m).
Its task is to work out how to protect US networks from disruption by the viruses, worms and hack attacks that have become commonplace.
Under Mr Yoran, a cyber alert system was set up to send out warnings about big hitting viruses and net attacks as they occur.
His sudden resignation, giving only a day's notice, led to suggestions that he felt frustrated by the lack of prominence given to cyber security in the wider homeland organisation.
"Amit Yoran's decision to leave after one year suggests that the current post of national cyber security director does not carry enough weight to get the job done," Harris Miller, president of the Information Technology Association of America, told the Reuters news agency.
An attempt by US politicians to pass a law to promote the work of the cyber security division within the homeland security structure is now mired in Congress.