Malwarebytes or Sophos or Both?

There is no reason to ever install or run any 3rd party "cleaning", "optimizing", "speed-up", anti-virus, VPN or security apps on your Mac.  This user tip describes what you need to know and do in order to protect your Mac: Effective defenses against malware and other threats - Apple Community.  

There are no known viruses, i.e. self propagating, for Macs.  There are, however, adware and malware which require the user to install although unwittingly most of the time thru sneaky links, etc.   

Anti Virus developers try to group all types as viruses into their ad campaigns of fear.  They do a poor job of the detecting and isolating the adware and malware.  Since there are no viruses these apps use up a lot of system resources searching for what is non-existent and adversely affect system and app performance.

There is one app, Malwarebytes, which was developed by a long time contributor to these forums and a highly respected member of the computer security community, that is designed solely to seek out adware and known malware and remove it.  The free version is more than adequate for most users. The free version doesn't run continuously in the background. You only run it when you feel you need to. That way it doesn't interfere with the system's performance by using CPU resources.  

P. Phillips wrote:

Any of the below should be removed as per Developers Instructions 

This will include BitDefender ,

There has been sufficient advise offered, from several Contributors, for the User to make an informed and educated choice what the next course of action is required.

The suggestions have been put forth on a volunteer basis, in good faith and in the best interests of the computer.

I never use 3rd party apps like that (although I did once install and run Malwarebytes and then deleted it). What I use: macOS - Security - Apple

Also see: Protect your Mac from malware - Apple Support

I wouldn't let sophos anywhere near my Mac. and while malwarebytes is ok for Macs, you will only want to use it when necessary. you should not leave it running in the background if you do install it.

as far as safety, you should read this informative apple community article: Effective defenses against malware and other threats - Apple Community

Two more Cents here

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. 

Additionally, and specific to Big Sur macOS 11 and Monterey macOS 12, the Operating System resides in a Sealed and Read Only Volume that can not be opened by the User or “ Bad Actor “ Software.

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.

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

Any of the below should be removed as per Developers Instructions 

This will include BitDefender ,

There has been sufficient advise offered, from several Contributors, for the User to make an informed and educated choice what the next course of action is required.

The suggestions have been put forth on a volunteer basis, in good faith and in the best interests of the computer.

I would not let any typical AV software anywhere near my Mac. Not Sophos, Norton, Bitdefender, Avast, or other. They are all useless as there are no viruses that can affect the Mac OS, and they do nothing to stop you from installing or running Trojans.

Malwarebytes is mostly an "after the fact" tool. That is, helping to remove adware and other malware you've already installed. In such cases, use it, then remove it.

Neither are necessary, or wanted.

MalwareBytes at least provides one useful function, that of removing Adware you've installed.

If I was to fall for some ruse and installed Adware, I'd use EtreCheck to remove it since doesn't install any other useless garbage with the app.

Something not mentioned about MalwareBytes. When you first install it, it runs in demo mode for a certain amount of time. Meaning, all cost features are enabled. Once that time has passed, it reverts to free mode. Which does nothing unless you choose to launch the app and run it.

The point of this is even in free mode, it will look for new definitions file when you launch it. So there's no need to remove it, then reinstall it later to get the "latest" version. It will otherwise just sit on the drive doing nothing until you choose to run it.

I do a manual scan every few months with the stand-alone BitDefender app, which is free, but it has never found any malware on my iMac (though I have had it find positives on Macs I support). It updates the latest definitions when you run the scan. Nothing to install, no background processes, just run the scan.

Hi,

I run Malwarebytes free version periodically. It is non-intrusive/doesn't install things on the Mac which could interfere with normal operations like other malware apps do.

Neither. All you need is the Mac's own built-in security and a bit of common sense.

I have Malwarebytes installed that I use very rarely but no issue leaving on my Mac.