Schmidt was the former chief of security at Microsoft Corp. before taking the post in February. He succeeded Richard Clarke, who had spent 11 years in the White House across three administrations, and was the president's counterterror coordinator at the time of the Sept. 11, 2001, attacks.
The White House confirmed Monday that Schmidt will leave at the end of the month to pursue private sector opportunities.
In an e-mail sent to staff and industry officials, Schmidt noted that many of his responsibilities have been transferred to the new Homeland Security Department.
"While significant progress has been made, there still is much to do," Schmidt said in the e-mail. "The nation as a whole is much better at responding to cyberattacks then at any time in the past, but cybersecurity cannot now be reduced to a `second tier' issue. It is not sufficient to just respond to attacks, but rather proactive measures must also be implemented to reduce vulnerabilities and prevent future attacks."
When Clarke announced his resignation, he also warned of future attacks on the Internet. "As long as we have vulnerabilities in cyberspace, and as long as America has enemies, we are at risk of the two coming together to severely damage our great country," he wrote.