What is onyX?

You don't need to install any anti-virus apps, cleaning apps, or third party security software on a Mac. These types of apps usually cause more problems than they solve plus they impact system performance. These types of apps interfere with the normal operation of macOS. macOS already has everything it needs to run well and be secure as long as you also do your part by practicing safe computing habits. Here is an article written by a well respected forum contributor with some guidelines:

Effective defenses against malware and other threats - Apple Community

1. It's an utility program which should only be used by people who understand what it does. It can be dangerous if misused.

2. You generally don't need anti-malware software in macOS.

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It's a so-called "helper" program that in the end can damage your system.

I found it useless as it did nothing my Mac didn't didn't need or didn't already do