Earlier quoted context omitted.
If your computer has any kind of secure boot / boot chain attestation stuff going on, like all phones do now, rebooting clears out pretty much all malware. Software bugs can put the system in to a bad state which can be abused by malware, but none of it can persist through a reboot since everything is checked and measured from scratch during the boot.
> Software bugs can put the system in to a bad state which can be abused by malware, but none of it can persist through a reboot since everything is checked and measured from scratch during the boot. This does not account for supply chain attacks nor trojan attacks which seek consensual installation. A reboot will not eradicate these threat vectors.
What we have seen is state funded hacking groups can often exploit bugs which break out of sandboxes and embed themselves in the system. But the malicious code only exists in memory, it can’t persist between reboots because the next boot would fail the checksum and signature checks.
Which is why security focused OSs will periodically reboot themselves to flush out possible malware and why jailbreaks and hacks for phones and game consoles usually have to be reinitiated after every boot.
MacOS has a few measures including SIP and boot chain security to implement this, though it’s currently hard to set up a properly secure Linux desktop.