Rc.common - T1163 (18d4ab39-12ed-4a16-9fdb-ae311bba4a0f)
During the boot process, macOS executes source /etc/rc.common, which is a shell script containing various utility functions. This file also defines routines for processing command-line arguments and for gathering system settings, and is thus recommended to include in the start of Startup Item Scripts (Citation: Startup Items). In macOS and OS X, this is now a deprecated technique in favor of launch agents and launch daemons, but is currently still used.
Adversaries can use the rc.common file as a way to hide code for persistence that will execute on each reboot as the root user (Citation: Methods of Mac Malware Persistence).