Prune at the link level. Connect to people you trust to do so using a special community (or really, physical infra). It is ok if bank A to bank B communication

Prune at the link level. Connect to people you trust to do so using a special community (or really, physical infra). It is ok if bank A to bank B communications get protected in a way which eliminates Bank A and Bank B connectivity to even 20% of legitimate end users in emergencies.