Depends on the constraints of the scenario. With "cold boot attacks", after you cut power to a machine the system's memory will still be readable for a brief m

Depends on the constraints of the scenario. With "cold boot attacks", after you cut power to a machine the system's memory will still be readable for a brief moment. If you chill the RAM with compressed air you can stave off the electrical self-discharge even longer. Boot to a specialized OS or move the memory to alternate hardware and you can dump its contents. These attacks specifically target disk encryption and other keys that are kept in memory.