One thing to make clear about the Equifax breach is that it wasn't caused by a single security update that was never applied, as has been put forward by Equifax

One thing to make clear about the Equifax breach is that it wasn't caused by a single security update that was never applied, as has been put forward by Equifax. It was caused by an insecure information architecture that let web front ends have direct database access. Good security requires defense in depth, not an unbreachable perimeter. Equifax's security was a failure long before it was hacked. Obviously the technical details may not be the appropriate level to discuss with Congress, but an analogy that they can understand might be helpful. What Equifax did was the equivalent of keeping the country's nuclear codes at an outpost in Afghanistan and then blaming a sentry for falling asleep when an enemy slipped in and stole them.