Helping people with computers... one answer at a time.

A quick scan is going to find a good percentage of malware problems. You should also consider a full scan at the right time.

My question concerns the defaults as established by software programs, especially security programs. I have an anti-virus firewall and anti-spyware program that comes with it. When I click to do a scan, there comes up a menu of Quick Scan or Complete Scan. The Quick Scan is always marked as the default operation. How do you feel about that? On occasion, I do a complete scan, but it doesn't seem to catch anymore than if I use a Quick Scan. The program is very well known and is usually in the top 10 of security programs. I don't want to give out the name for the program, so as not to influence any of your readers if this question is posed.

In this excerpt from Answercast #22, I look at the way anti-malware programs look for viruses and spyware and how that fits into a quick scan.

Is a Quick Scan okay?

So, no, it's not an issue. It's very common.

What we need to understand is the difference between a Quick Scan and a Complete Scan or a Full Scan.

Malware habits

Malware in general, depending on the kind of malware, whether you're talking spyware or viruses and so forth, tends to infect certain types of files in certain locations.

For example, they infect files that are installed as part of Windows. Or they infect files that are installed or referenced by the registry or only .exe files, that kind of thing.

What that means is that the anti-virus softwares, the anti-malware tools, can all make a couple of assumptions that allow you to cover 99% of all known malware by only scanning the areas where those malware typically infect.

Quick scan has a lot of benefit

So what you're really getting is a lot of benefit by doing a Quick Scan that only scans those areas; without having to spend all of this time scanning absolutely everything on your computer for very little additional benefit.

As you've seen, typically, a complete scan won't find anything more than a Quick Scan... only because the Quick Scan has already scanned all of the areas that typically have malware.

Complete malware scan

A complete scan, or a full scan, (as you might expect) scans absolutely every file on the hard disk that you're looking at. So it would scan your .doc files, your .mp3s, your .jpegs, your pictures, your music. The chances of there actually being malware in those files is so small that it makes a lot of sense to not bother scanning them. That's what a Quick Scan is all about.

Extra security

Typically, my recommendation is to be relatively secure and not make those kind of assumptions. Go ahead and run a Quick Scan when you're running a scan manually. But when a scan is run automatically, consider letting that be a full scan. It will take longer but it will happen in the background.

In my case, for example, I let it happen overnight. That way, you know that even that little tiny percentage of possibilities is not going to happen because you have scanned everything.

If you're scanning manually, you're probably interested in getting a fairly quick answer about whether or not your machine is infected. A Quick Scan is going to give you an answer with 99% accuracy within the scope of that particular anti-malware program.

So, it doesn't concern me at all. It's pretty much what I expect from almost every anti-malware tool regardless of which one you happen to be using.

End of Answercast #22 Back to - Audio Segment


Article C5413 - May 31, 2012 « »

Leo Leo A. Notenboom has been playing with computers since he was required to take a programming class in 1976. An 18 year career as a programmer at Microsoft soon followed. After "retiring" in 2001, Leo started Ask Leo! in 2003 as a place for answers to common computer and technical questions. More about Leo.

Not what you needed?

June 2, 2012 7:09 AM

Thanks for another very helpful article., Can you please bring presssure to bear on Microsoft to introduce a pause button on MSE, so that my pc can cool down when I am warrned that the hard drive is becomeing too hot?

Actually if you open MSE, in Settings/Scheduled Scan you can configur it to limit the CPU usage during that scan. That could help. However more important is that your computer is probably not getting enough cooling to handle the heat. MSE is simply showing a symptom of a problem with your system. Look into improving the ventilation.
June 2, 2012 8:16 AM

A heating hard drive is very serious. I hope you are backed up. If I were you I'd take immediate steps to figure out why it's heating up like that. Maybe it just needs to be cleaned, or moved so it gets more ventilation. But allowing it to overheat is heading towards disaster. It's not really MSE causing it. MSE is only triggering the issue.

Here's a nice article Leo wrote on heat, and it also has some good links at the bottom that will help you with troubleshooting the problem.

Does my computer use more power or generate more heat depending on what its doing?

And, I'm don't think Leo (or anyone for that matter) can call Microsoft up and tell them what to do! But that's a nice thought!

June 2, 2012 9:34 AM

@Connie. Many thanks for your comments. My machine is a tw0 year old laptop with 84 gigs used and plenty of space left. My external drive has 280 gigs on board out of a possible 500. It takes over an hour to run a full scan ( and a full image backukp later). Both drives receive warnings at over 42 degrees from Acronis Drive Monitor after about 30 minutes. The good news is that I now have Malwarebytes on board and that has a pause button available. Which is why I'm surprised that the techies at Microsoft did not include such a button on MSE.

I want to be clear about something: the fact that MSE has no pause button is not the problem. The fact that you feel you need a pause button is. Your machine should not overheat, and that's a problem that may very well cause you other issues down the road. The overheating should be addressed. A pause button, or using different software, does nothing to resolve the underlying problem.
June 2, 2012 11:43 AM

Thanks for the comment Leo. The warnings I get are about my internal and external hard drives. So will heat from the CPU cause the readings for the hard drives to be increased?

Everything "in the box" affects everything else in the same box. So the CPU heating up will cause the disk to be warmer, and vice versa. The external drive is heating up all on it's own. Both are potential problems.
June 2, 2012 1:42 PM

Thanks once more Leo.

June 6, 2012 10:02 PM

Gwyn, while you may have a ventilation problem, I believe most drives operate in the 35-50 degree Celcius range, with around 40 being the usual. I think you need to change the setting on Acronis to warn at over 50 degrees.

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