Iranian hackers reportedly breached the control system of a small dam just outside of New York City in 2013. The incident sparked concerns about cyber security vulnerabilities throughout the federal government, all the way to the White House.

Via the Wall Street Journal:

Iranian hackers infiltrated the control system of a small dam less than 20 miles from New York City two years ago, sparking concerns that reached to the White House, according to former and current U.S. officials and experts familiar with the previously undisclosed incident.

The breach came amid attacks by hackers linked to Iran’s government against the websites of U.S. banks, and just a few years after American spies had damaged an Iranian nuclear facility with a sophisticated computer worm called Stuxnet. In October 2012, then-Defense Secretary Leon Panetta called out Iran’s hacking, prompting fears of cyberwar.

The still-classified dam intrusion illustrates a top concern for U.S. officials as they enter an age of digital state-on-state conflict. America’s power grid, factories, pipelines, bridges and dams—all prime targets for digital armies—are sitting largely unprotected on the Internet. And, unlike in a traditional war, it is sometimes difficult to know whether or where an opponent has struck. In the case of the dam hack, federal investigators initially thought the target might have been a much larger dam in Oregon.

According to the report, the Iranian hackers didn’t overtake the system but “probed” it, likely seeking out weaknesses.

The White House website currently lists the Obama administration’s top five priorities regarding cyber security, number one being:

  1. Protecting the country’s critical infrastructure — our most important information systems — from cyber threats.

In 2011, the administration announced a Cybersecurity Legislative Proposal, designed to “protect our national security by addressing threats to our power grids, water systems, and other critical infrastructure.”

Despite causing no discernible harm, the cyber attack did revealed information “about how computers running the flood control system worked.”