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Do Virus Scanners Slow Down Your System?

Last response: in Reviews comments
November 30, 2010 5:30:29 AM

Great article, thanks!
November 30, 2010 5:31:12 AM

before i read the article, my guess is Norton is the slowest and most useless....
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November 30, 2010 5:41:25 AM

How can u forget Avira , it's so popular & so good .
November 30, 2010 5:43:05 AM

I guess the new ones are lighter than the earlier ones for some of them....
November 30, 2010 5:44:21 AM

well from my point of view - antivirus scanner do application loading to take a much longer time and this was proven by your tests.

I think that AV software has no place into todays operating systems except for inexperincied users. I'm investing money to fast SSD disc to improve performace, why the hell intstall AV software to push performance back?
November 30, 2010 5:45:25 AM

This is the kind of article that keeps me coming back to Tom's! Kudos!
November 30, 2010 5:48:16 AM

Avast please?
November 30, 2010 5:49:34 AM

talk about heavy modifications on the new set of AVs compared to the older ones ... my surprise is norton which i was expecting to cripple the system to a halt .... very nice article btw
November 30, 2010 5:50:39 AM

The test rig's CPU looks funny to me.

Athlon II X4 645
3.5 GHz, Quad-Core, 6 MB L3 Cache

Isn't that a Phenom?
November 30, 2010 6:00:46 AM

@Fip - Because when dirty viruses do their job, you'll get a headache.
November 30, 2010 6:05:32 AM

iam2thecrowebefore i read the article, my guess is Norton is the slowest and most useless....

well i am really surprised
November 30, 2010 6:19:51 AM

@tony singh
yes - for inexperienced user. I have no problem with viruses over 8 years. OS Patches, working under different than admin account, not using IE, and not executing every garbage downloaded from internet. And finally virtustotal page for testing for viruses if you realy need it.
November 30, 2010 6:24:54 AM

iam2thecrowewell i am really surprised

I get Norton Security Suite free with Comcast. I was kind of bummed when I found out that's all they have available, but so far its been good to me. I haven't noticed any adverse effects, maybe startup is s little slower.
November 30, 2010 6:31:29 AM

this is tested on a fresh install - the average system has a ~2 year old install and fragmentation and lower end hdd's, combind with a crapload of other software trying to startup - no really a real world benchmark.
November 30, 2010 6:31:47 AM

it would have been useful to see a difference in the benchmarks using different HDDs like the 5400 RPM laptop ones, 7200 RPM and SSDs, that would have made a difference
November 30, 2010 6:39:45 AM

Fip is right, cmon, it's not so easy to get a virus installed in your computer. Only real concern is about pendrive virus, otherwise, it's real hard get a virus actually, so just deactivate autorun and you're done.

If you still think a Anti-virus is useful, look to the logs of your anti-virus, how much viruses have you executed? How much of these you wouldn't figured out even without any anti-virus? A computer virus it's not something invisible who will eat your computer's guts, it's just a program, and need to you to execute him at least one time.

We aren't in 1996 with blaster or melissa. Tom's is supposed to be a site for tech guys, cmon, you aren't supposed to be a facebook brainless guy who don't know the difference betweek "naked gurls.exe" and "naked gurls.jpg".
November 30, 2010 6:43:09 AM

Well the biggest slowdown you will experience with antivirus software is when you open a folder full of exe files and explorer tries to show all the icons of the executables. There is a very noticeable slowdown in that case.
Also i would have liked a startup benchmark, because the antivirus also slowdowns somewhat the startup process.
November 30, 2010 6:44:10 AM

I think Microsoft Security Essentials should be included if possible and there is a situation that I think it is greatly affected by anti-virus software: Windows start-up.
November 30, 2010 6:58:46 AM

iam2thecrowewell i am really surprised

Norton has VASTLY improved compared to what it used to be. I use Norton 360, and I have to say that it has been a great product.
November 30, 2010 7:04:05 AM

2 ddragoonss
AV is far from 100% protection, and could bring new problems (recently ESET NOD Smart Security causes problem with internet connection due to connection inspection / filtering ... ) For IT Pro is risk to get a virus very low, and if get one - few hours to get it out is worh instead of years of boring my pc with AV software
November 30, 2010 7:10:49 AM

Great article cause I was also of the opinion that "antivirus" crap mess up your computer's performance.

My only dissapointement is that you dont show anything about Windows Defender which is free and convinient. Liked it more than AVG and the rest of the last crap i tried tbh. Now, as always I am not just virus free but also antivirus free cause I honestly dont like antivirus progs. I tend to format too often :) 
November 30, 2010 7:22:50 AM

November 30, 2010 7:23:24 AM

Meh. Overrated and not conducive to gamers while in game. I'd like to see FPS differences while in games for this review to be noteworthy.

I find active virus protection (resident shield) dropped me a few FPS - nothing major - but I don't need active protection while I'm in game; even if I do browse websites and multi-task. Also, file scanning while in game is really bad, regardless of the software or your computer's power. You always get lag - even if it's only a little - and it's always noticeable. I don't know how it affects SDD instead of HDD, but so far every HDD I've played on gets reduced framerates when the protection software is actively scanning files (and I use higher performance HDDs).

yes - for inexperienced user. I have no problem with viruses over 8 years. OS Patches, working under different than admin account, not using IE, and not executing every garbage downloaded from internet. And finally virtustotal page for testing for viruses if you realy need it.

Err, ya. Don't be so dismissively smug. I haven't had any major virus problems since Nimda was spread (and that was when I had Norton; big mistake trusting them): I update OS critical patches every 3-6 months (not very often); I've used my primary and sole user account (no seperation); I've used IE the entire time; obviously activeX and pop-ups are disabled.

The whole hate for IE is ridiculous. I've seen as many problems with Firefox as IE. It's not 2002 any more. You're not cool because you use Firefox because it's "not as well known" or "not rampantly targeted by trojans". Those reasons are absolutely not true any more.

I have resident shield off, no internet security, scan weekly with AVG Free (and usually cancel it after system files are scanned) and apparently I'm either extremely lucky or I just have a knack for not clicking where I shouldn't.

Oh, Norton is garbage. Not only does it fight with Windows to run your system and interrupt kernel processes, their resolve processes are crap as well. Also, everyone I've known that used or uses Norton has mentioned problems with it, regardless of being savvy or not.
November 30, 2010 7:30:33 AM

Without reading: Yes, they do. Kasperksy Business edition on a single core machine. Oh yeah, it slows down, a lot
November 30, 2010 7:32:23 AM


yes, problem with IE is history - but using Opera / Firefox was that, what helped me to live all these years with no problem.

To be honest - I have nothing to say against IE in win7 - it is really good, but i'm still using opera because i like it, and just because if there will be a security problem - IE will be still afected in first place, because it is so wide spread.
November 30, 2010 7:57:37 AM

fip___...IE will be still afected in first place, because it is so wide spread.

Touche. It also has the most financial support backing it. We could take that debate beyond the horizon and back.
November 30, 2010 8:01:52 AM

Gief stats for Eset NOD 32 and AVG please :)  otherwise great article thanks Tom :) 
November 30, 2010 8:12:43 AM

Ok, but what happens when you are in a game and your scheduled virus scan starts scanning the game files you are currently using ? Horrible lag.
November 30, 2010 8:13:40 AM

Try installing anti-virus software on this configuration and see what happens:
Intel Celeron M 360 @ 1.40GHz
512 MB RAM

I just want to point out that anti-virus software CANNOT be installed on all computers.
November 30, 2010 8:45:03 AM

Well missing benchmark for decompression of winrar file (this is where whole AV magic happens) and benchmarks with would show same result while system have to handle possible infection (ie. conficker or other virus from web/LAN)
November 30, 2010 8:45:41 AM

I would have liked to have seen a seen a less high spec system or two thrown into the mix, something along the lines of a dual or single core with 2GB of memory. These sort of systems are still very common and might have shown that it is worth upgrading.

Interesting as the information is, I wouldn't have expected the test system to struggle much with the extra burden. Still hats off as it has been ages since I have seen a test like this.
November 30, 2010 8:47:30 AM

Its really a fantastic article. I had some doubts but now all are clear.
November 30, 2010 8:53:17 AM

No ESET or NOD benches? I'm disappointed.
November 30, 2010 8:58:29 AM

Why was AVG 10 not used in the benchmarks? In my experience with hundreds of computers with every AV under the sun, all AV's will miss something that the competitor will catch. Of all the AV's, Norton was by far the biggest resource hog.
November 30, 2010 9:02:42 AM

Good article, I would of thought that AV's would use a little more resources than the article showed.

For most people reading on here and other tech sites regularly, AV may not be needed. But most people should have them. I use the free Avira AntiVir Personal and have the AntiVir guard disabled 99.9% of the time. I scan for viruses probably every 1-2 months since I'm not too worried about them, even then just in certain folders on my hard drives. I am more concerned about spyware and such and run Malwarebytes every month and sometimes SuperAntiSpyware if I download stuff I shouldn't probably be downloading in the first place.

Of course for a safer browsing experience, I use Sandboxie and a different Firefox install and feel very safe when I go look at "art" on the web :) 
Can also use NoScript, AdBlock Plus, and CookieSafe to name a few to be even more safe. Also Opera in Sandboxie works good. Of course I don't know if it's wise to have my regular Firefox going and then a Sandboxie Firefox one also, maybe a bug could cause some security thing through.

I think Virus Total is a great tool to use also. I seem to use that every 3 weeks or so. Especially easy if you have a hash checker integrated within Windows Explorer.

I did do a Google search 2 months ago and the 2nd site I clicked on gave a pop-up install virus thing, but got out of it. No, Google didn't have a warning on that site, must of been brand new
November 30, 2010 9:03:12 AM

Ubunduit would have been useful to see a difference in the benchmarks using different HDDs like the 5400 RPM laptop ones, 7200 RPM and SSDs, that would have made a difference

I think the benchmarks should have been done with a SSD since there I would expect the performance impact to be the worst.
If I would buy a blazing-fast SSD but end up with the same speed as with some lower-cost one due to AV SW, what would be the point of the price premium?
November 30, 2010 9:29:52 AM

Anychance of Adding Avast to the benchmark ?
November 30, 2010 9:47:41 AM

I wouldve liked to see MSE up there.
November 30, 2010 9:50:50 AM

why no Bitdefender?? Thats the stuff !!! fail
November 30, 2010 9:55:07 AM

Biased article. On a typical cheap (and mostly outdated) low-end office box AV means severe slow down, not only due to CPU usage but the added memory overhead, which leads to extra swapping. On the rig used, which is by no means a cheap one, the tests could never point a different result. It's like Microsoft's methodology to say their newest Windows version is faster than all the previous ones.
November 30, 2010 10:15:34 AM

aznshinobiAvast please?

+1. Avast free edition is what I used for everything
November 30, 2010 10:31:53 AM

Interesting choice of using the picture for MSE even though it wasn't included in your tests (at least I didn't see it). I also didn't see anything about booting the machine ... I've had both AVG and MSE installed at different times on my 1.7gHz, 1G ram HP (laptop, circa 2005). During boot up, having either of these installed brings my machine to its knees. Your benchmarks might say one thing, but my real world experience tells me otherwise. I generally get a good read from the tests that I read here, but this one fell a little short IMO. People with a quad core 3.5 gHz machine of course aren't going to see a major system impact. The people with the older hardware on the other hand...
November 30, 2010 10:37:22 AM

this is bullshit, test playing games and make a scan in your pc while gaming
when u will have a pain in ur a** a lot of stuttering and lag, other thing to take into account
not everybody have a 4quad core in their pc, and less in a office enveroment
so what are u testing?
Antivirus software slowdown ur system like 10-20% in everything u do.

November 30, 2010 10:44:36 AM

You should and could have included Avira Antivir and Avast antivirus in those benches.
November 30, 2010 10:51:37 AM

These test are not a surprise to me and i don't complaint about having an AV active.
What i complaint is the windows boot time which i think it's really affected by AV load and first scan to critical files and memory, which is usually active on standard configurations on most computers.
This is the test i'd like to see. Boot time without AV and with AV active with standard configuration and first scan.
November 30, 2010 10:53:49 AM

I don't bother with resident virus scanners. A linux live cd with a scanner will do the job manually. My CPU (P4 2.8ghz) is just too slow to have a resident scanner. I make regular images of my boot drive, so if i get a virus I can't clean with the live cd, I just restore a backup image.
I haven't got a virus in over 3 years.

If you have low FPS in a game due to slow CPU, you can't afford any background tasks.
November 30, 2010 10:56:43 AM

Excellent article. Should have included more anti-virus software.
November 30, 2010 11:29:20 AM

Avira is one of the best, and is free for home users.

It should be included.