The websites of Bank of America, JPMorgan Chase, Wells Fargo, and other U.S. financial institutions suffered simultaneous outages due to a coordinated denial of service cyberattack in September 2012. Attackers flooded bank servers with junk traffic, preventing users from online banking. An Iranian group called Izz ad-Din al-Qassam Cyber Fighters initially claimed responsibility for the incident. At the time, the media reported that U.S. intelligence believed the denial of service was in response to U.S. imposed economic sanctions to counter Iran’s nuclear program. Seven Iranian individuals linked to the Islamic Revolutionary Guard Corps were eventually indicted by the U.S. Department of Justice in 2016 for their involvement in the incident.  The denial of service attacks against U.S. banks is significant for two reasons. First, the size and scale of the attacks led the State Department to seek other countries’ assistance in taking down the compromised computers that were flooding the banks with junk traffic. Second, the attacks would indicate that Iran—if it was in fact using the attacks as retaliation for U.S. financial sanctions—was acting proportionally in its dispute with the United States.