The recently retired director of the National Security Agency is defending his bid to develop a new cybersecurity model for paying clients, saying his approach doesn't derive from work he did for the government.

Keith Alexander retired in March from dual jobs as NSA chief and head of the military's cyber command. He says his new company is seeking to patent a cybersecurity technology he created with partners after leaving government.

The retired general spent nearly 40 years in public service. He says there is nothing improper about working in a field he knows something about.

Alexander asks, if an Army brain surgeon retires from the military, can't he still get paid to perform brain surgery in private practice?