Shawn Henry, the FBI's executive assistant director, has decided to retire after 24 years of service with the bureau, according to FBI officials. The announcement was made by FBI deputy director Sean Joyce in a message to FBI officials and senior leaders.

Henry has been the bureau's outspoken top agent on cybersecurity issues, credited with boosting the FBI's computer crime and cybersecurity capabilities.  Henry led an effort to establish the National Cyber Investigative Joint Task Force (NCIJTF), and formed partnerships and posted agents in Amsterdam, Romania and Estonia.

During his tenure Henry has overseen major computer crime and cybersecurity investigations that have spanned the globe from denial-of-service attacks (malicious commands that flood sites and  networks with requests for information, making the networks and websites unavailable to computer users), to major bank breaches. In recent years cyber cases have taken on increasing complexity with major intrusions into Google, the IMF, the RSA corporation and NASDAQ along with major hacking breaches by "hacktivist" groups such as Anonymous and Lulzsec.

Earlier this week the FBI arrested members of Anonymous and disclosed that a top leader in the group Lulzsec had been working as an FBI informant.

"I believe the cyber threat is an existential one, meaning that a major cyber attack could potentially wipe out whole companies. It could shut down our electric grid or water supply. It could cause serious damage to parts of our cities, and ultimately even kill people," Henry said in an October 2011 speech in Baltimore.

"While it may sound alarmist, the threat is incredibly real, and intrusions into corporate networks, personal computers, and government systems are occurring every single day by the thousands," Henry said.

Henry served as the assistant director of the FBI's cyber division from 2008 to 2010, when he was then promoted to assistant director in charge of the FBI's Washington field office. (Henry had begun his career in the FBI as a special agent in the Washington field office in 1989.) After serving as the head of the Washington field office for less than a year, Henry was pulled back to headquarters by  FBI director Robert Mueller to be the executive assistant director of the Criminal, Cyber, Response, and Services Branch.

Last fall Henry highlighted the damage a cyber attack had on a major high-tech firm.

"One company that was recently the victim of an intrusion determined it had lost 10 years' worth of research and development, valued at $1 billion, virtually overnight," Henry said in the October Baltimore speech.

In the same speech Henry discussed the possibility of creating an alternate closed internet for financial and critical infrastructure systems. "Under the current Internet structure, we can't tech our way out of the cyber threat."

Henry will be taking a job in the private sector but FBI officials would not disclose where he was heading.