Dive Brief: About 25% of power utilities were exposed to the SolarWinds hack, officials at the North American Electric Reliability Corp. (NERC) said on Tuesday, though no subsequent activity from hackers was detected beyond the initial breach. A much smaller number of utilities revealed that the vulnerability reached into operational technology (OT) and industrial control systems, but NERC said overall there were few operational impacts from the attack. Security experts warn it may be too soon to tell, however, if all of the SolarWinds impacts and vulnerabilities have been found or addressed. The White House is rushing to develop a plan to protect the United States' grid, including from supply chain vulnerabilities like the SolarWinds breakdown. Bloomberg reported on a draft of the plan, which includes an examination of vulnerabilities in grid components, incentives for security upgrades and an audit of high-impact points in utility systems.