Do Virus Scanners Slow Down Your System?

General Use Benchmarks

It can be difficult to define and measure the general responsiveness of a PC, yet the productivity and communications benchmarks that are part of the PCMark Vantage suite are probably well-suited for this test.

The PCMark Vantage communications benchmark includes a combination of tests that cover common tasks like data encryption, compression, Web page rendering, and Windows Mail searches. Past experience with PCMark shows that the margin of error can be a little larger than what we’d like it to be and the score with no security software running is actually lower than some results when virus scanners and Internet security suites are running. We consequently can’t draw any conclusions from these results, but can see that there isn’t a large difference when any of these products are used.

The productivity benchmark suite includes common tasks like starting applications, editing documents in WordPad, and searching contacts using Windows Search. There is a multitasking portion of this benchmark that runs three simultaneous tasks, including a Windows Contact search and Windows Mail message rules and renders numerous Web pages in Internet Explorer. Finally, this bench includes a number of hard disk stressing tasks, such as a Windows Defender scan and a boot timer.

As you can see, there are definitely some strong trends here that suggest this benchmark is affected by security software to varying degrees, but Kaspersky and Trend Micro products appear to suffer a large performance penalty.

Let’s dig deeper into the PCMark productivity benchmark specifically to see exactly what tasks are running slower when antivirus software installed:

Very interesting. First, let’s look at the productivity tasks that are not affected by the presence of these scanners. All of the hard disk-intensive tasks, such as Windows Vista startup, Windows Defender, and application loading, perform no differently with or without security software installed. This result supports our previous hard drive test results that also demonstrate little or no performance penalties due to a resident virus scanner. Aside from this, text editing a Word document also shows no performance differential.

On the other hand, a Windows Contacts search operation demonstrates a sizable performance penalty when Kaspersky or Trend Micro security software is installed. Note that the Productivity 4 Windows Contacts search occurs during multitasking, but both results are similar. The other operation that appears to be affected by the presence of security software is Web page rendering, also recorded during multi-tasking operations.

On a final note, we should mention that we left one of the PCMark productivity benchmarks out of the above chart. The Productivity 4 Windows Mail copying benchmark provides very inconsistent results in our testing, reporting anywhere between one and six operations per second.

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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