For an industry increasingly reliant on gadgets such as digital sensors, infrared cameras and drones to monitor security and check for leaks, the sabotage illustrated how vulnerable pipelines are to low-tech attacks.
On Tuesday, climate activists broke through fences and cut locks and chains simultaneously in several states and simply turned the pipelines off.
All they had to do was twist shut giant valves on five cross-border pipelines that together can send 2.8 million barrels a day of crude to the United States from Canada - equal to about 15 percent of daily U.S. consumption.
The activists did no damage to the pipelines, which operating companies shut down as a precaution for checks before restarting.
The United States is the world's largest energy market, and the infrastructure to drill, refine, store and deliver that energy to consumers is connected by millions of miles of pipeline that are impossible to protect entirely from attack.
"You're not manning these things on a permanent basis. It's not viable," said Stewart Dewar, a project manager at Senstar, an Ottawa-based company that authored a 2012 white paper on pipeline security. "It's too expensive."
There are more than 200,000 miles (322,000 km) of oil lines and many times that of natural gas lines across the United States. Thousands of rural and often remote pumping and valve stations dot the country.
The cost of posting armed guards at valve stations, usually found every 20 miles along the underground pipelines, would be prohibitive, said Dewar.
For companies, there are few options to police the parts of their pipeline networks that sit above ground, such as the valve stations.