Random Malware?!

That is absolutely the worst advice ever...For the OP, stay away from "mackeeper," "as if it were a swarm of bees."

Read: Effective defenses against malware and ot… - Apple Community for some great advice.

Relying on any security software to prevent any and all malware will eventually fail, every - single - time. No matter what it is, it can only detect and remove what it knows about.

MalwareBytes is pretty much the only Mac software for this type of thing any experienced Mac user will recommend. But it isn't, and can't be perfect. You can't rely on it to allow you to install anything and everything you feel like and, somehow, have perfect protection. That will never happen.

And just to repeat what's already been said, stay away from MacKeeper as if it were a nuclear bomb less than 5 seconds from going off. The company has been sued - twice - for its false and misleading claims. And they still do it. You can put MacKeeper on a brand new Mac out of the box, and it will say you have dozens of serious issues. All of which can be "fixed" if you simply pay for a completely worthless subscription.

After all that, yes, you did download and install something, or it wouldn't be there. There are no Mac viruses (malware that self replicates). Virtually everything is a Trojan (malware YOU must install in some manner). No AV software of any kind, including MalwareBytes, will stop you from installing a Trojan. MalwareBytes may recognize something you've installed after the fact, but not necessarily. It still comes down to how new of a threat it is.

I did not refer to MalwareBytes. It is often recommended in these communities and it does the job. I was referring to antivirus and other cleaning apps that run in the background using system resources while providing no benefit and causing issues.

Sites like downloads.com include this junk because they get paid for every download that includes the adware. It's not considered "bad" because adware is just that. It clogs and slows down your computer with relentless ads, but nothing truly malicious.

I do visit such sites when I'm looking for a particular type of software. But I will not download anything from such file aggregate sites. I get the names of the software I want to try and then find the web site of vendor who makes it. Then download it directly from them.

it seems that malware and adware got installed while surfing web

i recommend installing mackeeper stopad extension to both safari and chrome

Do not install MacKeeper or any other third party app that claims to clean, protect, etc.