They attacked the firmware of customer terminals on the ground via a management network, not the satellites themselves.

See, among others:

https://www.viasat.com/about/newsroom/blog/ka-sat-network-cy...

https://www.reversemode.com/2022/03/viasat-incident-from-spe...

The terminal firmware had a bunch of security vulnerabilities allowing injection of arbitrary executables and commands without adequate signature verification.

The attack bricked the terminals requiring a hardware swap to restore service.

They didn't hack the satellites, they hacked the modems:

> "After those modems were knocked offline it wasn't like you unplug them and plug them back in and reboot and they come back,"

Would it be possible to return the favour and hack Russian satellites?