Is my anti-malware setup consistent with "best practices"?

Question

A few days ago, my PC was acting weird and froze sometimes. I did full scans using Avast! Free Antivirus and Malwarebytes Anti-Malware since I assumed it was a virus causing these, but both software didn't find any threat. I also used the Microsoft Safety Scanner. I did a quick scan at first and it didn't find any threat. I did a full scan but when the bar that shows progress was almost full, I refreshed my desktop which caused the whole PC to freeze. When I force powered off by holding the power button and turned it on, it was normal.

Since three security applications didn't find any threat, I started to wonder whether they were enough to ensure that my PC is free from viruses.

Here are the security applications installed on my PC:

• Avast! Antivirus
• Malwarebytes Anti-Malware
• Malwarebytes Anti-Exploit
• Windows Firewall

My questions:

• Are the three scans enough?
• Is my security setup strong enough? If not, should I remove something or add something?
• I heard about Spybot Search and Destroy but am not familiar with it or its reputation. Is it another similar anti-malware application (i.e., would it provide incremental benefits or just duplicate what I am already running)?

I'm using Windows 10 Single Language.

Please note that I am not looking for an opinion poll. Rather, I'm seeking input from people with specific knowledge about malware protection on what is considered best and sufficient practices.

Answer 1

I regret to inform you that there is no software that exists that can guarantee you that there are no viruses on your computer. You can say it's unlikely, but can not get a guarantee. Here's why, software is reactive. If I wrote a virus right this minute, would your software know how to detect it? No, it doesn't know what to look for. The antivirus creator hasn't told the software how to identify my virus. What if you made it look for certain functions? That's great until a piece of legitimate software uses that function and triggers a false positive. At this point you checked for viruses and other malware. You've found none. Time to check for other issues (drivers, startup programs, misconfigurations, hardware failures).

Answer 2

Memory testing:
Memtest is good, if you can make it run/boot on your hardware (I had trouble last time I tried).

For virus and malware scanning: turn off your computer for a few minutes, then BOOT from a separate media that hasn't been attached to your computer in the last month or so.

If you don't do this; the virus or malware may be "so mean" that it avoids detection. You have to either find unaffected media (with a virus/malware scanner) or create a new copy on another (trusted) computer.

Example "rescue CD" to download and put on CD/DVD (using a "safe" computer) - then boot and run:
https://www.f-secure.com/en/web/labs_global/tools-beta