Do Virus Scanners Slow Down Your System?

Conclusion: A Pleasant Surprise

As mentioned on the first page, I came into this story idea aware that I had a prejudiced expectation. Although I’d never actually tested it for myself, I was under the impression that the presence of a resident virus scanner would have an adverse effect on system performance.

I’m very happy to report that my preconceptions have no place in today’s PC world, as even single-core processors are able to demonstrate comparable performance with or without modern security software installed. This is true not only for basic virus scanners, but also for comprehensive security suites.

Having said that, it’s also true that the presence of security software isn’t undetectable in all circumstances. We do see an increase in application launch times with a virus scanner installed, but the only significant wait time is a couple seconds added on the first launch of a program. Subsequent launches appear to be cached, and the wait time is almost imperceptible.

The only benchmark that shows a notable performance decrease with a virus scanner installed is PCMark’s productivity suite. Even here the performance hit is only notable with two of the 10 tested security products, and in this case, an increase in Windows Contacts search times is the main cause. While I can’t speak for everyone I know, I do not spend a significant amount of time searching Windows Contacts, so for me this isn’t much of an issue.

While these results are encouraging, a couple of questions need to be answered. As we mentioned at the beginning, we’ve limited our testing to performance with the virus scanner installed. However, what is the performance hit during an actual virus scan? This is something we hope to examine in a follow-up review in the near future.

However, for the time being, we’ve learned that a user can confidently install a virus scanner or Internet security suite without being too concerned about performance consequences. It appears that typical tasks we undertake when using our PCs will not be notably slowed by the security software on which we rely. In the end, I’m pleased to admit that my expectation of a decrease in general PC performance when a virus scanner is installed was incorrect and obsolete.

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  • theshonen8899
    Great article, thanks!
  • iam2thecrowe
    before i read the article, my guess is Norton is the slowest and most useless....
  • tony singh
    How can u forget Avira , it's so popular & so good .
  • alyoshka
    I guess the new ones are lighter than the earlier ones for some of them....
  • 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?
  • ruffopurititiwang
    This is the kind of article that keeps me coming back to Tom's! Kudos!
  • aznshinobi
    Avast please?
  • micr0be
    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
  • 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?
  • tony singh
    @Fip - Because when dirty viruses do their job, you'll get a headache.
  • iam2thecrowe
    iam2thecrowebefore i read the article, my guess is Norton is the slowest and most useless....

    well i am really surprised
  • @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.
  • takeapieandrun
    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.
  • apache_lives
    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.
  • 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
  • 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".
  • 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.
  • Hupiscratch
    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.
  • cjl
    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.
  • 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
  • Manos
    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 :)
  • karma831
    No MSE?
  • pandemonium_ctp
    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.
  • damianrobertjones
    Without reading: Yes, they do. Kasperksy Business edition on a single core machine. Oh yeah, it slows down, a lot