Do Virus Scanners Slow Down Your System?

Test System And Benchmarks

We begin by selecting the security software to test. We're curious to find out if Internet security suites might contain bloatware that could slow down a system more than a simple anti-virus program would, so we've included not only virus scanners, but also complete Internet security suites offered by noteworthy developers. This means we’re testing AVG Anti-Virus, AVG Internet Security, Kaspersky Anti-Virus, Kaspersky Internet Security, McAfee VirusScan Plus, McAfee Internet Security, Norton AntiVirus, Norton Internet Security, Trend Micro Titanium AntiVirus+, and Trend Micro Titanium Internet Security. [edit: we originally listed some obsolete versions of the AV software. The programs we actually tested were the newest available versions as of October, 2010]

Where benchmarks are concerned, we’ve assembled a suite of tests to exercise most aspects of PC performance, from gaming to office work. We’re testing raw application performance and also the time it takes for the system to respond to boot and to program launch requests. In order to do this, we’ve even developed some custom benchmarks, courtesy of our own Andrew Ku.

While we're running the benchmarks on an Athlon II X4 645, we'll be disabling two of the CPU cores for the majority of benchmarks. As a result, most of the benchmarks reflect the performance users can expect from a budget dual-core CPU. On page seven we run more benchmarks with only a single CPU core enabled, and also with all four CPU cores enabled, to see if the performance burden changes based on the number of execution cores available to the system.

With all this in mind, here are the particulars for our test system and benchmarks:

  Test System
MotherboardAsus M4A785TD-V EVO
Socket AM3, AMD 785G, BIOS 0410
ProcessorAthlon II X4 645
3.1 GHz, Quad-Core CPU
Multiplier set to 3.0 GHz
Single- and quad-cores enabled for CPU core comparison on page 7
CPU Cooler
Cooler Master Hyper TX3
MemoryCrucial DDR3-1333
Dual-Channel 2 x 2048 MB, 669 MHz,
CAS 9-9-9-24-1T
GraphicsRadeon HD 5830 Reference
1 GB GDDR5, 800 MHz GPU, 1000 MHz Memory
Hard DriveWestern Digital Caviar Black 1000 GB
7200 RPM, 32 MB Cache SATA 3Gb/s
Software and Drivers
Operating System
Microsoft Windows 7 x64
DirectX Version
DirectX 11
Graphics DriversAMD Catalyst 10.9

And here's a list of the benchmarks:

Benchmark Configuration
3D Games
CrysisPatch 1.2.1, DirectX 10, 64-bit executable, benchmark tool
High Quality, No AA
Audio/Video Encoding
TMPGEnc 4.0 ExpressVersion:
Import File: "Terminator 2" SE DVD (5 Minutes)
Resolution: 720x576 (PAL) 16:9
Xvid 1.2.2Display encoding status = off
WinRAR 3.90Version x64 3.90, Dictionary = 4096 KB, Benchmark: THG-Workload (334 MB)
Synthetic Benchmarks
PCMark VantageVersion: x64, All Benchmarks
SiSoftware Sandra 2010Version 2010.1.16.11, CPU Test = CPU Arithmetic
Create a new thread in the US Reviews comments forum about this subject
This thread is closed for comments
Comment from the forums
    Your comment
    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.
  • aznshinobi
    Avast please?
  • iam2thecrowe
    before i read the article, my guess is Norton is the slowest and most useless....
  • Other Comments
  • 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....
  • 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?
  • 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
  • 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?
  • 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
  • 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.
  • 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.
  • 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
  • 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".
  • 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.
  • 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.
  • Anonymous
    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