Great memory @Ewebute ! that was the "Sunburst hack " or...

Great memory @Ewebute ! that was the "Sunburst hack " or malicious code was inserted in the form of a Dll into a Solarwinds update.
As soon as Solarwind clients ran the update a Trojan was also installed on the computer where the update was run.
As Solarwinds is a network monitoring tool the Solarwinds device probably had access from outside your network via a firewall.
This is where your firewall rules could have kept you safe ie: to prevent the outside bad actor from opening a specific port to his Trojan from an external I/P address. Not sure what the impact was as about 18,000 firms were running Solarwinds at the time ???