how to check for adware and malware on a mac ios 10.15.3

Do you need anti-virus on your Mac?

No, you do not.

MacOS is very secure and quite capable of keeping itself that way. There is no need to run any cleaning, speed-up or optimizing apps, nor any anti-virus apps.

In fact, most anti-virals and cleaning apps are less than helpful on the Mac and often cause more problems and headache than they prevent because they conflict with the Mac’s built in securities.

Please see these Apple Support Community documents:

Effective Defenses Against Malware - Apple Community

How to install adware - Apple Community

Avoid phishing emails, fake 'virus' alerts…and other scams - Apple Community 

macOS security built right in. - Apple 

If you currently have this type of app installed, you should uninstall it according to the developer's instructions, and continue to use best practices when using your Mac.

How do you check for adware and malware?

If you have been advised as a troubleshooting measure to do a malware scan on your Mac, then Malwarebytes is a safe and recommended utility, often recommended by Apple support techs. And the free version is all you need to get started.

Also, if your Mac is misbehaving, EtreCheck can help us help you by eliminating us from having to ask you a ton of questions:

EtreCheck is a diagnostic app that gathers and reports important debugging information about your Macintosh. It is very highly regarded and meant to be used with Apple Support Communities to help others help you troubleshoot and resolve your Mac problems.

Please navigate to the Mac App Store OR to EtreCheck.com and download the free version of EtreCheck. Once you’ve run the app and created your report please post it with your reply to this message. 

For instructions on how to attach your EtreCheck report to your reply, please click  How to use Add Text when posting…

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

You have installed some of the worst malware known on macOS.

Uninstall Norton and your Mac will run much better and actually be more secure as it is not around to interfere with the OS's built-in protection. Just look at the plethora of Symantec or Norton system modifications it installed. Nothing could be expected to run well with all of that crap larded into the system.

You also installed the second worst malware for macOS, MacKeeper, but I don't see any evidence it is still installed.

I don't know what Mac Upper is, but Etrecheck didn't flag it, but it sounds like Adware. It looks like you tried to uninstall it, but you didn't use the developer's installer as the LaunchDaemon still exists. The EtreCheck report should have a link to allow you to "Clean up" the leftovers.

I'd use an antivirus, though other dear users here would not.

Get an antivirus, it can help you scan malware and adware etc.

Viruses sometimes steal developer licenses that are real, therefore bypassing macOS default protection.

Also what if macOS suddenly has a "pandemic"? Those with antiviruses will be protected.

I'd still recommend getting an antivirus to scan malware, don't manually do it. You may forget to delete some virus files if you do.

You apparently didn't post the report correctly.

Use the Share Report button and select Copy Report.

Then, start a reply here, click the Additional Text button here (document icon), and paste in the report.