A rule that only allowed the Solarwinds server access to the Internet if it was using the OIP protocol AND using the FQDN [api.solarwinds.com](https://api.solarwinds.com) would have protected any network.
Hindsight can teach us something here.
We need to be very selective at what traffic we are allowing out from critical systems. If we need telemetry or updates we need to be able to whitelist these explicitly.
If you follow this simple suggestion the next backdoor we discover like this will be completely blocked by YOUR firewall.