Why it isn’t a good idea to run multiple full antivirus products at the same time

Why it isn’t a good idea to run multiple full antivirus products at the same time

why-not-to-use-multiple-anti-malware-blog

You’ve probably heard it before: Never run two antivirus programs at the same time, it’s trouble!

But what’s the logic behind this?

Is it sound advice based on technical reasoning? Or is it just a feeble marketing attempt by antivirus companies to dissuade you from installing competitors’ products on your PC?

Admittedly, some vendors in our industry use questionable methods to make some easy cash. However, that’s not the driving reason behind this principle, which has been around for more than a decade. Let’s take a look beneath the surface of protection software.

1. Chain reactions: Endless scan loops

While this was mainly a problem in the early years of antivirus software, it’s still worth mentioning. In those days, antivirus software typically scanned all files that were being accessed on your computer to check for any dangerous programs you may have had lying around that could cause you grief if you happened to start them up.

In simple tech terms: The operating system would signal that a file was being read when you viewed it in Explorer. Then the first antivirus would read the file to scan it with its signatures/matching patterns. That file reading action would trigger another file-access signal by the operating system, which would tell the second antivirus to scan the file too. But while the second antivirus read the file, a new independent signal would be triggered that forced the first antivirus to scan the file again, and so on. As a result, both antivirus products would re-scan files in an endless loop until all system resources were used up and the computer became inoperable.

Fortunately, that problem is mostly wiped out today. The industry has developed strategies to avoid such loops, and files are typically not scanned on each read action anymore, but only when they are newly created, started or modified.

2. Complexity issues: Potential incompatibilities

Modern antivirus/antimalware software acts like an extra layer that sits between the base of the operating system and the apps and programs that run on it. Developing this type of software isn’t trivial and requires many years of experience due to the sheer number of variables to consider. Protection programs are created in many different ways and often developers don’t stick to recommended coding standards. In particular, the use of undocumented operating system interfaces often cause unexpected crashes or freezes that are very difficult to resolve.

Sometimes it’s difficult to tell whether some vendors don’t have the required expertise to create their products in a way that makes them compatible with others, or if they simply don’t care and expect their customers to sort the problems out on their own.

We at Emsisoft always try to make our product compatible with as many others as possible and as some of our early users may still remember, our products were once even sold as ‘additional protection’ to classic antivirus products.c

3. Both detect a threat: Who is first to quarantine?

Imagine you have two antivirus products with real-time scans enabled. You download a dangerous file and both detect and alert a threat. But which is first to quarantine or remove the threat? You may encounter error messages as files suddenly disappear for one of the two programs as they attempt to quarantine. The best case scenario is that you’re left feeling confused; in the worst case scenario, neither of the antivirus are able to successfully quarantine the threat!

4. More isn’t always more: Little advantage for high resource cost

This is actually the strongest reason against running two full protection systems simultaneously. Virus/malware protection products today are rather complex and the exponentially growing number of threats (it doubles every year) requires a lot of code to keep the computer safe. This naturally results in a relatively high usage of computer resources, especially its memory (RAM). By running two full antivirus programs all the time, you’re basically wasting resources, because 90 percent or more of their functionality will be the same. All available protection products of reputable vendors today operate on very high quality standards and detection rates often only differ by about 1-2 percent according to test labs.

So, you might end up spending 0.5 to 1 GB or more of your available RAM to bring your detection rate up from, say, 98 percent to 99 percent. But is this minuscule improvement really worth it? Every new file on the computer would need to be scanned by both products, triggering two complex sets of code that use a lot of your CPU time, which could undoubtedly be better used for other tasks – you know, stuff you actually want to do on the computer.

The better option is to go for one product that comes with multiple scanning engines that are tuned to work together seamlessly, or a product that uses a layered protection approach with different technologies, or, better still, a product that implements both.

Our recommendation: Use only one protection

Do yourself a favor and avoid installing two full antivirus/antimalware products. It’s not worth it. If you have strong protection software that you are happy with, stick with it. If you are unhappy with it, uninstall it and then install a new one.

Don’t fall for free offerings. Even if the software doesn’t cost anything, it doesn’t necessarily make sense to add it to an already working security strategy.

Go for a complete antivirus/antimalware product that comes with layered protection and implements surf protection, file monitoring, behavior blocking and anti-ransomware modules that complement each other well. Emsisoft Anti-Malware bundles all of them and even adds a second full antivirus scanner, which is integrated on a very deep technical level to avoid all the problems of having two scanners that we described earlier.

Occasionally run second opinion scans

We encourage you to check your protected system with a second opinion scanner from time to time, just to be sure that your main antivirus/antimalware hasn’t missed anything. Scanner-only products typically don’t have any issues running alongside protection products so it’s safe to use them.

Cloud based scanners are nice light-weight options here. Alternatively, if you’re not using Emsisoft Anti-Malware to protect your computer, you can use our free Emsisoft Emergency Kit, which is the only fully featured dual-engine scanner available and doesn’t even require installation to check your PC for threats and unwanted programs (PUPs).

Have a malware-free day!

  • Crusty Ole Fool

    Malwarebytes claims that it can run concurrently with other Antivirus programs.
    I have used Malwarebytes, Premium along side Avast, Free and haven’t experienced any ill effects.

    • Terryw45

      Malwarebytes is one step behind, I agree, only one Anti Virus prog, not to sure Emsi is the best, but their advertisement guru is up there with the best of them, you pays your money, you takes your choice! One size does not fit all.

      • ArnsteinBjone

        Exactly my thougts when I read the post; “…but their advertisement guru is up there with the best of them…” :-)

        But, for some reason, I belive in Emsisoft. I can’t really put my finger on the deciding point. Competence? People with proper education? People with a hearth for what they do?

        I have been a computer nerd since 1983 (I’m 62) , and I have tried a lot of security software, often 2 or multiple running simultaneously. I have now had only Emsisoft for a year, and I feel very safe. I haven’t questioned/double-checked any of the software’s decisions. It just works well, as far as I can tell.

        P.s. I’m also the kind of guy that use both belt and suspenders :-) I have 14 TB of private cloud backup (2×3+2×4), i.e. backup of backup + one, untouchable and locked.

    • Bob Pegram

      With my limited knowledge, I thought Malwarebytes checks for everything except viruses. That would be why it doesn’t conflict with antivirus software. I am not sure though.
      I know anti-spyware programs like SuperAntiSpyware and Spybot among others don’t conflict with antivirus porograms for that reason.

      • David Biggar

        To the best of my knowledge regarding Malwarebytes’ products, you are correct. Conflicts can still happen, but they are much less likely if there is no functional overlap.

    • Malwarebytes is AV since version 3, it recommends not to run any other AV alongside it.

      • Crusty Ole Fool

        I’ve read all 44 pages of the “Malwarebytes User Guide” for ver.3.3 and the only reference I can find is that “…the free AV that comes with modern operating systems, in conjunction with Malwarebytes is all you will ever need.”

        • Google: Announcing Malwarebytes 3.0, a next-generation antivirus replacement / Their blog post says, you can run other AV alongside it, but they say, you do not need it and on the forums, they do not really recommend it now, considering that it has problems with itself.

    • fitnes npng

      Ide advise you to look up what kind of data that or other AVs are leaching from you and compare it to Emsi soft, google about things you install because if a program scans your pc it means it knows everything its installed now it could be emsi is also doing it but havent found any evidence on it but in 2013 or 14 a reputable source checked what AVs leach from you and avast steals almost everything it can and what do you think they do with that info, sell it and make big cash from that, its what most AVs do if you think logically, emsi soft is one of the few to be as honest about their company, you can see that in “about” page of a site of an AV app and youll see about honesty of alot of AVs, most are not 100% with the users, kaspersky and bitdefender are same as avast.

      • Crusty Ole Fool

        I tried running Emsi instead of Avast but it slowed everything down way too much. Start-up was just shy of 2 minutes. New tabs in browsers (both Chrome and FF) were so long I would begin to wonder if the link was broke.
        I’m all over the Internet, do most of my financials on line and in 20 years have never had a breach. On rare occasions there is a surprise advert in my “In Box” but only occasionally. I do daily,weekly and monthly maintenance routines using a variety of programs to clear PUPs, PUMs and unwanted cookies as well as checking for any stealth installations.

        • Christian

          Did you completely uninstall Avast before you installed Emsisoft Anti-Malware? Your described slowdowns are typically a result of having two programs. Even if they are visually shut down, their drivers may still be active and interfere with each other. Emsisoft Anti-Malware running standalone shouldn’t slow down anything to a noticeable level.

          • Crusty Ole Fool

            When I installed Emsi AV the only thing running was Win7 Pro. I even shutdown the Win. Firewall prior to installation.
            I tried two installations, about 9 mo.s to a year apart. The last was about a year ago.

          • Christian

            Would you be willing to help us investigate in that issue? It seems to be a rare condition, but it should be fixed. Please email to [email protected] so they can guide you through some options for locating the source of the problem.

        • Naruto Uzumaki

          what npng was saying isnt something you can shut off or do anything but uninstall the program, and about the slow downs, did you try the ram optimize setting in emsisoft? If so then i dont know why its not running well, i have it on win 10 and it works great no slow downs at all, I am on an ssd though so it probably has something to do with it but still, maybe contact support about it because it sure shouldnt be doing that. Good luck!

    • LGBT

      Malwarebytes is an Anti-Malware, it’s designed to work alongside an Anti-Virus, they really aren’t that different, but in most cases you can use Malwarebytes with another security program.

      • MBAM was… Now with “Malwarebytes For Windows”, they clearly sell it as a full AV, especially since it integrates MBAE, which may has detrimental effects if used alongside other products also offering anti-exploit features.
        Anyway the era of the “companion real-time AV model” is long gone.

  • Tom Hunt

    When I was in the computer repair business, I would find home computers that had four or five AV programs in and running. This would load down the system to the point nothing useful would get done. Also, weird and unpredictable things would happen to the OS software. People use to load down their systems with every available maintenance free programs they found on the Internet at the first sign of a problem causing all sorts of problems. Dealing with the non technical public was a pain. This is one of the reasons I terminated my business this past January after 12 years and 45 years in the computer repair business.

  • dufas_duck

    So, we should get rid of Microsoft Security Essentials because it interferes with Emsisoft software???

    • hello @dufas_duck:disqus the MSE on Windows 7?

      If yes, personally i would remove it and use only Emsisoft as main solution, not only because it may interferes but because its just a basic scanner that afford nothing much compared to other solutions available.

      • dufas_duck

        Actually, I.m one of those people that you are against. I have 5 anti-virus/malware programs on my system…….only they are turned off except one. The one that is running warns me about problems and usually cleans them out.

        Reason for the others??? I have found that no anti-‘whatever’ program catches every attack, even Emsisoft misses problems.

        When I get hit with a virus, I manually run another scan individually of a couple of other programs. I usually find problems that were missed by Emsisoft [as an example] or any of the other scanners….

        So, technically, I am only running one ant-virus program, I guess it depends on how one uses them…wouldn’t you say???

        • “I have 5 anti-virus/malware programs on my system…….only they are turned off except one […] So, technically, I am only running one ant-virus program, I guess it depends on how one uses them…wouldn’t you say???”

          Technically no. Even if they may not conflict right away because you turned some off, their drivers and services are still active and may still create issues not visible, and anyway they still waste resources (via their services, active processes like the one for the gui or engine, etc….)..
          What creates issues is not the AV being turned-on or off, it is often because of the drivers.

          Why not select one real-time AV and use On-Demand scanners?
          Those don’t run in the background, don’t waste your machines resources, don’t conflict. So you can have many of them. I have 5 of them, i can run one after the other when needed while using Emsisoft as the only real-time scanner.

          • dufas_duck

            You remind me of a used car salesman.. The other 4 anti-virus programs are completely tuned off until needed. They do not show up in task manager or msconfig or the startup log……

  • Nevi Løvfelt

    It’s a shame, but Malwarebytes is not what it was 4-5 years ago.I dont know what went wrong, but it’s not the problem solver it was. Today I only use Emsi and Webroot. One at a time. As on demand scanner I use Emsisofts emergency app. Free and extremely effective.

  • Rui Machado

    And what about the Windows Defender on Windows 10 and Emsisoft? Can tehy run concurrently?

    • Hello @disqus_D238HMYdpD:disqus i tried for a short time, i didn’t see any conflict, but i prefer just stay with Emsisoft, don’t want waste resources just for it especially when Windows Defender isn’t very light…

    • Christian

      I personally wouldn’t consider Windows Defender a full antivirus/antimalware. It’s a baseline protection at best, which is also what Microsoft suggests. You mostly can run it next to antivirus, but it typically doesn’t add much in terms of protection.

  • Alca Traz

    Obviously, every anti-virus company will do their best to sell their product. Unless they have a business death wish, they will tout their own one as being the best choice. Since Windows 10 came along, I’ve stuck with Defender. It was right there already, completely integrated, free, and continuously updated in the background. So far, during the 2 yrs, a few viruses have been shot down and quarantined, and it would appear that no virus has got past it. Once in while I run a free anti-malware app. Many stray pups have been found and sent to the great kennels in the sky. Altogether a very simple and efficient setup. You could say ‘a howling success’ :)

  • Robert Colin

    I have run two antivirus programs to find that they both missed malware and crashed my system. I now run only Emsisoft that is definitely the best option and a pleasure to use recommended.

    • Hello @disqus_IiLz68Am45:disqus,
      Indeed, it is what i often observe, people use 2+ AVs at same time, everything is ok when nothing happen in the system, but when an infection occurs then the problems appears.
      It is like riding with 2 bikes at same time, on a straight line road, sure you can do well, but when you engage in a slope… ^^

  • ArnsteinBjone

    Terryw45 said in the comments here: “…but their advertisement guru is up there with the best of them…”
    Exactly my thoughts when I read the post :-))

    But, for some reason, I belive in Emsisoft anyway. I can’t really put my finger on the deciding point.
    Competence? People with proper education? People with a hearth for what they do?

    I have been a computer nerd since 1983 (I’m 62) , and I have tried a lot of security software, often 2 or multiple running simultaneously. I have now had only Emsisoft for a year, and I feel very safe. I haven’t questioned/double-checked any of the software’s decisions. It just works well, as far as I can tell.

    P.s. I’m also the kind of guy that use both belt and suspenders :-) : I have 14 TB of private cloud backup (2×3+2×4), i.e. backup of backup + one, untouchable and locked. (I’m a photographer, architect and a structural engineer. I need to access previous work from time to time, 10-20 years back in time…)

  • Diego pietro

    TOP THREE ANTIVIRUSES
    Emsisoft,Malwarebytes and Avira

  • Diego pietro

    Avast is not that good proctecting

  • Robert carl

    Contact Cybervenom6 via gmail for anything. Criminal records and bank loans are all gone

  • DrHanibalLecter

    My problem with emsisoft is simple:

    When I go to their page I feel totally bullshitted by a button that tells me “Free Download”

    As the software itself is of course not free, which is NOT a problem, this is a blatant attempt to trick people. Why would I want anything to do with a company that tells me “We think you are a moron!”

    • Fabian Wosar

      You are aware that Emsisoft Anti-Malware is available in a free version, right? Once your license or trial runs out, it reverts automatically into free mode. The free version allows you to scan for and remove infections and is functionally equivalent to EEK but still offers convenience of a permanently installed application, like context menu integration for example.

  • diwul62

    To be honest…
    This blog post makes me uncertain (again), specifically with regards to using Malwarebytes.

    As for any other AV application: I agree, don’t use multiple AV applications, due to potential conflicts.

    But AFAIK Malwarebytes conveniently works together with other AV products. At least they say so.
    I use both Emsisoft and Malwarebytes Premium for quite a number of years and never encountered any issues. Am I just lucky then?
    I do have the Malwarebytes-folder excluded from being monitored by Emsisoft (Settings->Exclusions->Exclude from monitoring).

    That said, I do have the feeling that Malwarebytes intercepts/blocks ‘unsafe websites’ more often than Emsisoft. When MB blocks a site, there is no similar warning from Emsisoft. Shouldn’t there be two pop-ups then?
    But maybe it is a matter of finetuning Emsisoft(?)

    • hello @diwul62:disqus

      “but AFAIK Malwarebytes conveniently works together with other AV products. At least they say so. I use both Emsisoft and Malwarebytes Premium for quite a number of years and never encountered any issues. Am I just lucky then?”

      It was viable in the past, but now Malwarebytes is changing its stand and clearly announced that from now on their product will be a standalone one.

      “That said, I do have the feeling that Malwarebytes intercepts/blocks ‘unsafe websites’ more often than Emsisoft. When MB blocks a site, there is no similar warning from Emsisoft. Shouldn’t there be two pop-ups then?
      But maybe it is a matter of finetuning Emsisoft(?)”

      We surely have different lists, also it may depend which soft detect the site first, if MBAM block a site first, so since you don’t access it anymore, Emsisoft probably won’t alert.
      there is a lot of factors to consider.