(Discussion) Malware returning after removal?

[Will_49]

So I recently published a thread where one of my PCs started running slowly, especially opening Chrome. Sr-71 suggested an anti-malware scan, which I did with Zemana. Everything came out clear. However, earlier today, Zemana detected a virus (no new downloads or anything). So it got me thinking, can viruses in the form of extensions hide themselves from scans? It is very strange that it was not detected the first time, any thoughts?

 

[Dark Lord of Tech]

It might have been that Zemana accessed it's updates and found it because of the new signatures.