Why is a full scan taking so long?

leftisthominid

I recently switched to BitDefender. My first scan took several hours (I don't know how long, since I had to cancel and restart the scan midway through). A few days later, I ended up doing another scan and it finished within 40 minutes.

Today, I ran Spybot Anti Beacon to disable Windows telemetry/tracking. On a lark, I decided to run another scan. It hasn't found anything, but it is going for over three hours now. 

What is with the discrepancy in scan lengths?

Wortex

Yes, because Installed applications that have been scanned and deemed as safe will not be repeatedly scanned, unless their behavior has either changed or a malicious intent has been spotted. As such, only unknown applications will be scrutinized by the full spectrum of antimalware technologies.