Do Virus Scanners Slow Down Your System?

Single-, Dual-, And Quad-Core Benchmarks

We think it’s important to address one of the variables missing from our previous tests, and that is hardware. As we’ve seen up until this point, most applications don’t seem to show a notable difference in performance, regardless of whether security software is installed or not. But all of the tests have also been run on a dual-core CPU, too. Will the results change on a single- or quad-core processor?

We would expect the raw performance to drop slightly in multithreaded applications. But we're curious about the effect security software has on single-core performance, too. While we don’t have time to run the entire benchmark suite for different processor setups, we run all three CPU options with AVG AntiVirus 9, AVG Internet Security 9, and without any security software installed for a quick test:

While the number of available execution cores can certainly affect the raw results, when it comes to comparing performance on the basis of available compute resources, the only metric that shows a significant performance drop associated with a single-core processor running security software is the time it takes to load Internet pages on the first run. Aside from that, security software doesn’t seem to have an adverse affect on single-core PCs. This is a surprising result, as we expected security software to take advantage of threading. It’s possible that our test scenarios don’t give the software an ideal opportunity to do so, but it’s a surprising result nonetheless.

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239 comments
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    Top Comments
  • 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.
    38
  • aznshinobi
    Avast please?
    33
  • iam2thecrowe
    before i read the article, my guess is Norton is the slowest and most useless....
    24
  • Other Comments
  • theshonen8899
    Great article, thanks!
    5
  • iam2thecrowe
    before i read the article, my guess is Norton is the slowest and most useless....
    24
  • tony singh
    How can u forget Avira , it's so popular & so good .
    24
  • alyoshka
    I guess the new ones are lighter than the earlier ones for some of them....
    -3
  • Anonymous
    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?
    -21
  • ruffopurititiwang
    This is the kind of article that keeps me coming back to Tom's! Kudos!
    4
  • aznshinobi
    Avast please?
    33
  • 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
    4
  • Anonymous
    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?
    -12
  • tony singh
    @Fip - Because when dirty viruses do their job, you'll get a headache.
    2
  • iam2thecrowe
    iam2thecrowebefore i read the article, my guess is Norton is the slowest and most useless....

    well i am really surprised
    13
  • Anonymous
    @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.
    -11
  • 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.
    2
  • 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.
    24
  • Anonymous
    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
    9
  • Anonymous
    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".
    -13
  • Anonymous
    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.
    4
  • 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.
    38
  • 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.
    5
  • Anonymous
    2 ddragoonss
    thanks,
    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
    -7