The hack on Colonial Pipeline is being seen as one of the most significant attacks on critical national infrastructure in history.
The pipeline transports nearly half of the east coast's fuel supplies and prices at pumps are expected to rise if the outage is long lasting.
How can a pipeline be hacked?
For many people, the image of the oil industry is one of pipes, pumps and greasy black liquid.
In truth, the type of modern operation Colonial Pipeline runs is extremely digital.
Pressure sensors, thermostats, valves and pumps are used to monitor and control the flow of diesel, petrol and jet fuel across hundreds of miles of piping.
Colonial even has a high-tech "smart pig" (pipeline inspection gauge) robot that scurries through its pipes checking for anomalies.