do i need antivirus software

Anti-virus on a mac typically interferes with Mac own built in GateKeeper:

Gatekeeper mechanism, central to security services, which tries to ensure that any code loaded is ‘safe’. Code signatures are only part of this.

XProtect checks the security and integrity of files, including in broader ways too, vulnerable document types, such as JPEG images, are also screened to ensure that they’re not malicious.

Apple’s Malware Removal Tool (MRT) an app which often complements XProtect’s signature-based screening, and can automatically remove all traces of many different species of malware.

System Integrity Protection (SIP) which ensures that nothing can tamper with key system files, or even Apple’s bundled apps.

No such product is required, however the article has pertinent information.

Effective defenses against malware and ot… - Apple Community