Multiple runs of Smart Scan

I have a disk filled with various malware from a hacker class that I took. I copied this disk to a folder on my C: drive before installing NOD32. After installing the product I ran a Smart Scan. If identified 269 instances of infected files. I opted to delete them and it said that it cleaned them. Then I turned around and ran it again. This time it found 219 files from the same folders and I cleaned them. Ran it a third time and this time it found 3 from the same folder and this time apparently cleaned them without my intervention. The fourth time I ran it, nothing new was found.

Why did the smart scan behave in this manner? Why did it not find all of the files the first time through and why on the last time it found files, did it apparently clean them without my intervention?

 

Here are some possible explanations however, without more details on the exact process that took place I can only speak in generalities.

Some malicious files and applications require a reboot to be removed. I noticed that you did not mention any reboots in your process. If you scan and attempt to remove all detected files some may require a reboot to remove, while others will be deleted on the spot.

I also see you mentioned a Smart scan. Is it possible you ran scans with different scan options? As you know there are many types of malicious files out there. For Example, potentially unwanted applications have to be selected in the scan options in order to be detected.

You indeed could have different cleaning behaviors when running scans. For example, one scan is run with the option for strict cleaning and another scan is not. With strict cleaning you will not receive a prompt asking for action, as you have already specified the action to be taken.

 

I don't remember if I did a reboot between scans. If the program would have prompted me to do so, I would have. Each of the scans was as Smart Scan and I just opened the window and selected smart scan each time without tweaking any of the options.

I'll load it up again and try this once more.