The nation’s maritime ports handle more than $1.3 trillion in cargo each year. A disruption at any one of these ports could have a significant economic impact. This statement addresses: (a) cyber-related threats facing the maritime port environment; and (b) steps that the U.S. Department of Homeland Security (DHS) has taken to address cybersecurity in that environment.
http://www.gao.gov/assets/680/672973.pdf