Hi,
I'll shed some light on this. You are absolutely correct that you should never run 2 AV's at once. However, Malwarebytes is not classified as an Antivirus. It's classified as Antimalware. Just like you can run an Anti-USB infection program (MCShield) alongside Avast! and Malwarebytes. All 3 programs deal with 3 different infection types.
Malwarebytes has a read on this:
https://blog.malwarebytes.com/101/2015/09/whats-the-difference-between-antivirus-and-anti-malware/Some of the highlights if you haven't had time to read the post.
A virus is a piece of code that is capable of copying itself in order to do damage to your computer, including corrupting your system or destroying data. Malware, on the other hand, is an umbrella term that stands for a variety of malicious software, including Trojans, spyware, worms, adware, ransomware, and yes, viruses. So the logic follows: all viruses are malware. Not all malware are viruses. Ya dig?
Antivirus usually deals with the older, more established threats, such as Trojans, viruses, and worms. Anti-malware, by contrast, typically focuses on newer stuff, such as polymorphic malware and malware delivered by zero-day exploits. Antivirus protects users from lingering, predictable-yet-still-dangerous malware.
Your best bet is to use an antivirus program to catch the classic threats and an anti-malware program, like Malwarebytes Premium, for the newer, more advanced dangers. And you needn’t worry about the impact of running two real-time scanners at the same time on your machine’s performance—most anti-malware software is lightweight, easy-to-run, and designed to work alongside antivirus.
As a side note: It's always best practice to obtain software from the company website where possible. It's a lot harder to download bloarware on a website that isn't filled with advertisments with false download buttons. (Though I should note there is nothing legally wrong with CNET to my knowledge.)
MBAM >>
https://www.malwarebytes.com/
