Satellite communications, a critical part of many everyday functions, are not as secure as we might think they are. These communications are critical for organizing mass transit, military communications, emergency services, and more.
The attacks that could compromise a single satellite are very simple, some as simple as sending an SMS. And once one is compromised, a whole network could be brought down.
Apparently, recent research indicates that satellite firmware often has hardcoded credentials, backdoors, and weak protocols. While an attacker would have to have some knowledge of the firmware to accurately exploit it, gaining access would not be a problem for them.