The funny thing is that Spybot, Avast and Windows Defender didnt notice anything wrong. Only malwarebytes was able to finde the malware. However, I am currently reinstalling my PC.
Have you considered using another computer with a freshly installed Operating System for Bitcoin and Bitcoin only? Preferably one with a freshly installed and properly verified Linux Distribution. Windows is WAY more likely to become infected than a Linux Distribution is.
Unfortunately, sometimes there will be a few victims before somebody finally reports the infected file and the companies finally start recognizing it as malicious. Maybe you were the victim of a fresh malware. Also. Did you have all Spybot, Windows Defender, Avast and Malwarebytes installed and running at the same time? It sounds like a disaster that was waiting to happen!
If you still want to continue using Windows for your Bitcoin holdings, make sure the copy you are installing is genuine. Running a pirated copy of Windows can also put you at risk.