antivirus software

None.

There is no need to run any anti-virus, “cleaning”, “speed-up” or “optimizing” apps. In fact, most anti-virus 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.

macOS - Security - Apple

https://www.apple.com/macos/security/

Please also see these Apple Support Community documents:

click> Effective Defenses Against Malware (John Galt)- Apple Community

click> How to install adware (John Galt)- Apple Community

click> Avoid phishing emails, fake 'virus' alerts…and other scams - Apple Support

That question generally brings contentious replies, I for one do not think at the moment any is needed, but the bad guys are mostly all looking for the prize!

I run Malwarebytes once in awhile to check, & have tested most AV Apps for Mac, if you have a lot of friends running Windows & or you get a lot spam, you may want something to prevent spreading bad things to your Windows buddies... ClamXAV, Avira, etc.

Do not install any third party antivirus apps. They use system resources while providing no benefit. They interfere with the MacOS built-in protections and they may cause problems.

Included as potentially problamatic are AVIRA and all other third party antivirus apps.