iMac is shutting down

DAYALA wrote:

I have been plugging several external hard drives, one at a time. I ran etresoft

Unsigned filesThere are unsigned software files installed that could be malicious and should be reviewed.ReviewKernel panicsThis system has experienced kernel panics. This could be a sign of hardware failure.Review.

More than one antivirus appThis computer has multiple antivirus apps installed.ReviewApps crashingThere have been numerous app crashes.ReviewApps with heavy CPU usageThere have been numerous cases of apps with heavy CPU usage.ReviewClean upThere are orphan files that could be removed.ReviewSystem modificationsThere are a large number of system modifications running in the background.ReviewKernel extensions presentThis computer has kernel extensions that may not work in the future.Review

Part 1 of 2

Once this type of software are installed and embedded into the computer 

Start Over from Scratch 

Heavy Handed ?  - Yes 

Effective  ? - Yes 

For Apple Silicon computer >> Use Disk Utility to erase a Mac with Apple silicon.

Always make a Time Machine Backup  before  proceeding 

Emphasis on User Account Only

If going this route - I suggest Not using Startup Assist to migrate everything back.

This will probably Re-Introduce ( any questionable Third Party Software ) back into the Operating System . 

Part 2 of 2

Third Party Security Software 

There are no known Windows-like Viruses in the wild that self replicate and affect macOS, because of the underling UNIX  Foundation and Permission Limitation. 

The Operating System resides in a Sealed and Read Only Volume that cannot be opened by the User nor by Third Party Applications.

The Only thing this Antivirus software is protecting is the Bank Account of the Developers and for zero return to the User aside from the problems this software creates.

Mac app security enhancements

The Built in Security  is all that is required to protect the computer.

Protecting against malware in macOS

I understand.

Panics are very often caused by faulty hardware.

Have you any external devices connected to your iMac?

Hubs/docks, drives, optical drives, etc.

I suggest you disconnect everything and run the computer without any of them for a little while to see if that has any effect on the problem. If it does, then you can start reconnecting your external devices, one at a time, until the problem returns. This process may help you find the problem

Meanwhile, there is a software tool that we can use to troubleshoot the issue by getting a diagnostic look at your Mac hardware and its software load. Please run an EtreCheck (free) evaluation of your Mac and post the generated report back here in a reply. EtreCheck is a safe and highly regarded utility from a trusted developer and respected ASC contributor. The report it generates will not include any personal info. It simply gathers specifics about hardware performance and installed software that might be in conflict with the OS.

Please navigate to EtreCheck.com to download the utility. Be sure to Allow Full Disk Access when you install the app. Once you’ve run the app and created your report please post it with your reply to this message. 

Please note you must upload the full report. To see how, please click >  How to use Add Text when posting… EtreCheck Report.

We’ll use your EtreCheck report to look for the things that may be causing your problem and advise how to correct them.

Have you any idea the capacity of your startup drive and how much space is available?

You can go to System Settings > General > Storage for the info. If you have too little space available then macOS may have trouble running the computer properly. Ideally one should keep ~10%-15% of the total startup drive capacity as free space, or at very minimum ~50 GB always.

If space available or free is the problem, you'll have to find a way to move some stuff off the drive to another storage device.

You'll get the most accurate read of your free space in Disk Utility.

DAYALA wrote:

I have been plugging several external hard drives, one at a time. I ran etresoft

Unsigned filesThere are unsigned software files installed that could be malicious and should be reviewed.ReviewKernel panicsThis system has experienced kernel panics. This could be a sign of hardware failure.Review.

More than one antivirus appThis computer has multiple antivirus apps installed.ReviewApps crashingThere have been numerous app crashes.ReviewApps with heavy CPU usageThere have been numerous cases of apps with heavy CPU usage.ReviewClean upThere are orphan files that could be removed.ReviewSystem modificationsThere are a large number of system modifications running in the background.ReviewKernel extensions presentThis computer has kernel extensions that may not work in the future.Review

It's a start. 👍🏽

Please review this link to see how to post the full report in its entirety:

  How to use Add Text when posting… EtreCheck Report.

Meanwhile you've given is a big clue already:

You have more than one antivirus app installed.

This is never a good idea. Apps of this type and a few others (VPN, cleaning, optimizing and security apps) are often implicated in a Mac's poor performance and bad behavior. Third party antivirus in particular can interfere with macOS's own built in XProtect antivirus. Apple keeps XProtect updated regularly and the best thing you can do to help protect yourself is simply keep macOS updated.

Who better know’s how to protect your Mac and macOS than Apple?

Apple Platform Security - Apple Support

Protecting against malware in macOS - Apple Support

So, don't just disable it, uninstall that added antivirus.

Then reboot your Mac and use it for a bit and see if that has any effect.

And see about posting the entire Etrecheck report. There are potential clues in that full report... but no personal info.

DAYALA wrote:

I have been plugging several external hard drives, one at a time. I ran etresoft

…

.Kernel extensions presentThis computer has kernel extensions that may not work in the future.Review

Third-party kernel extensions are most likely causing the panics. Uninstall the kernel extensions using tge developer’s uninstaller and check for panics. If it still panics after you uninstall all of them, it is most likely a hardware fault that must be evaluated/repaired by Apple or Authorized Service Center.

Starting up in Safe Mode will disable third-party kernel extensions, so if it doesn’t panic in Safe Mode, it is a kernel extension.