President Obama emphasised cybersecurity while campaigning
The White House's acting cyber-security tsar has resigned from her post, according to the Wall Street Journal.
Melissa Hathaway told the paper she was standing down for "personal reasons" and would return to the private sector.
The former strategist was appointed as acting national cyber-adviser in February and was expected to be offered the post full time.
President Barack Obama has said that cyber-security is a high priority for his administration.
In May, the President announced plans for securing American computer networks against cyber attacks.
In recent years, US government and military bodies have reported attempts to infiltrate systems by hackers.
He announced the creation of a cyber-security office in the White House, and said he would personally appoint a "cyber-tsar".
Ms Hathaway was widely regarded as the person to fill that post after taking on the role as acting senior director for cyberspace for the National Security and Homeland Security Councils in February.
She completed a review of cyber-security for the Obama administration in April.
At the time, Ms Hathaway said the job ahead was "a marathon, not a sprint."
Her successor has not yet been named by the White House.