Don't bother with it or any such software. It is not needed.

• Apple always finds a way to improve performance or to get rid of bottlenecks that plague your Mac. Either way, unless your Mac is hopelessly outdated or not supported anymore, the latest macOS updates tend to make things run smoother. To check for updates, open the Mac App Store and click on the Updates category. Install updates for everything that you see listed there.
• It is possible to experience, for example, your Avast SecureLine VPN not connecting, speed problems, issues in China, problematic support, no anonymous payment method, not to mention possible security and privacy issues.
• Don't install Avast on your mac because these free antivirus programs are designed to distrupt your mac.İ was installed Avast 2 months ago and last week my mac is malfunctioned but i was fixed my mac.İ'm not advise the free antiviruses for mac that is free.

Jun 29, 2016  Features Avast Free Antivirus for Mac offers numerous, configurable features. The free features include an antivirus scanner, a firewall, reports, and that’s it. Scan – Avast offers a free antivirus scanner that you can use to scan files, folders, hard drives, and your computer. Avast Free Antivirus for Mac 8.0 could make a good fallback for monitoring known Mac malware, although our tests suggest it can slow your Mac to a crawl in daily activities when simply running in the background. Your Mac is not immune to threats — yet. Our free Mac antivirus protects on 3 fronts. Malware isn’t the only threat to your Mac. Malicious websites and vulnerable Wi-Fi networks can also jeopardize your safety. Avast Security provides essential free protection against all 3 threats, and our new. Let your Mac work as it was designed to work, without burdening it with worthless trash. I installed Avast 'free antivirus' on a brand new Mac containing nothing other than one minimally configured User account. It found hundreds of problems including 'decompression bombs' corrupted archives, 'too big to be processed' and 'unknown errors'.

Helpful Links Regarding Malware Problems

If you are having an immediate problem with ads popping up see The Safe Mac » Adware Removal Guide and The Safe Mac » Adware Removal Tool.

Open Safari, select Preferences from the Safari menu. Click on Extensions icon in the toolbar. Disable all Extensions. If this stops your problem, then re-enable them one by one until the problem returns. Now remove that extension as it is causing the problem.

An excellent link to read is Tom Reed's Mac Malware Guide.

Also, visit The XLab FAQs and read Detecting and avoiding malware and spyware.

See these Apple articles:

If you require anti-virus protection Thomas Reed recommends using ClamXAV. (Thank you to Thomas Reed for this recommendation.)

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From user Joe Bailey comes this equally useful advice:

The facts are:

1. There is no anti-malware software that can detect 100% of the malware out there.

2. There is no anti-malware that can detect everything targeting the Mac.

3. The very best way to prevent the most attacks is for you as the user to be aware that

the most successful malware attacks rely on very sophisticated social engineering

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techniques preying on human avarice, ****, and fear.

4. Internet popups saying the FBI, NSA, Microsoft, your ISP has detected malware on

your computer is intended to entice you to install their malware thinking it is a

protection against malware.

5. Some of the anti-malware products on the market are worse than the malware

from which they purport to protect you.

6. Be cautious where you go on the internet.

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7. Only download anything from sites you know are safe.

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8. Avoid links you receive in email, always be suspicious even if you get something

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you think is from a friend, but you were not expecting.

9. If there is any question in your mind, then assume it is malware.