A senior Pentagon official will outline the anatomy of a 2008 attack on its military's Central Command system, which he admits was triggered by a booby-trapped thumb drive.
Malicious code, which escaped US security systems, had found its way into key Defense networks after the thumb-drive was inserted into a laptop in the field.
The trap helped expose US war plans in Iraq and Afghanistan and has been described as the "most significant" military security breach in history.
"That code spread undetected on both classified and unclassified systems, establishing what amounted to a digital beachhead, from which data could be transferred to servers under foreign control," US Deputy Defense Secretary William J Lynn III, wrote in an essay for Foreign Affairs previewed by the New York Times and Washington Post.
Lynn declassified the security incident in an effort to raise the level of concern in the US congress over military information security, pointing to both hacker and supply chain threats as additional complexities to protecting 7 million devices and 15,000 networks from infiltration.
The Defense Department had banned CDs, USB drives and other removable media after the 2008 incident, however partially lifted the ban earlier this year.