System trying to modify files? What is system?

I got this notice today.

I blocked and terminated it.

I find it strange how it’s a vaguely named “system” which wants to modify my computer instead of an .exe file.
What is system, and what does it do? Is it a virus?

SYSTEM is PID 4 and its the Windows Kernel. This virtual process contains all running kernel-mode drivers. This also includes Windows File Sharing, HTTP.SYS and probably all virus scanners.

Unfortunately, file handle accounting is only done at process level, so you won’t be able to get additional information.

Unless there’s a reason to believe your system has been compromised, I’d allow and remember that. If you can’t trust the Windows Kernel what can you trust? Bupkis.