A recently discovered Linux malware with backdoor capabilities has flown under the radar for years, allowing attackers to harvest and exfiltrate sensitive information from compromised devices.
If you target a binary for dropping a backdoor you usually want to build a binary that runs everywhere. My guess is that they could figure out how to build a drop-in systemd that they could compile once and worked on all major distros. This would be much harder with the kernel itself.
Regarding how it is setup: Often backdoors & exploits are sold in packages and combined when attacking the victims. Depending on the group behind the specific attack, the exploit used for setup may be different on each deployment.
If you target a binary for dropping a backdoor you usually want to build a binary that runs everywhere. My guess is that they could figure out how to build a drop-in systemd that they could compile once and worked on all major distros. This would be much harder with the kernel itself.
Regarding how it is setup: Often backdoors & exploits are sold in packages and combined when attacking the victims. Depending on the group behind the specific attack, the exploit used for setup may be different on each deployment.