I have windows 7, 64 bit, running two antivirus:

  • Malwarebytes Pro + Malwarebytes Anti Rootkit
  • Avg 2013 internet security (Anti Rootkit included)

I had an issue yesterday and a user here on Super User told me:

"It's a Bad Idea to run two antivirus suites on one PC, the main reason is because they don't know about each other. Just choose the one you trust more"

But I don't trust any, and here's why, I used to run AVG, it rarely finds anything, and the firewall rarely blocks anything, MWB firewall blocks many sites, and usually finds more malware.

However, it's not always like that, yesterday for example, MWB found 15 malware, no rootkit. Just to be sure, I scanned the pc again using AVG, it found 7 more malware, including at least 2 rootkits.

By the way, I scan every program that I download twice, with AVG and MWB, never found a virus by scanning the downloaded files, and I use ad blocker, and I use Gmail which has the most advance spam filter, I only read few messages from my inbox, mark many as spams, and Chrome is my browser. I don't think I can secure my PC more than that!

I have some questions:

  • Is it a bad idea to run more than one antivirus on the same PC?
  • How far should one go to secure his PC? Where is the line between security and being paranoid?
  • Is trusting one Antivirus a good idea? I use two of the most well known antivirus, can't trust any.

closed as primarily opinion-based by Ƭᴇcʜιᴇ007, bwDraco, Tog, Breakthrough, Dave M Sep 5 '13 at 12:50

Many good questions generate some degree of opinion based on expert experience, but answers to this question will tend to be almost entirely based on opinions, rather than facts, references, or specific expertise. If this question can be reworded to fit the rules in the help center, please edit the question.

  • 4
    You are not running 2 antivirus suites, you are running 1 antivirus suite (giving real-time protection) & 1 on-demand scanner, alongside 1 anti-rootkit scanner. If however you were running 2 anti virus suites (both offering real time protection) eg AVG internet security suite & Norton Internet Security suite, there would be a conflict - and this would be a bad idea. – Simon Sep 1 '13 at 17:33
  • 1
    Just to add to my comments above.......You can have as many on-demand scanners as you like, but to run more than one internet security suite offering real time protection on your PC, is of no benefit what so ever. Which internet security suite you choose is entirely up to you: the majority now offer a free 30 day trial, for you to try, with no payment necessary. If you don't like it, just uninstall & try another one, until you find one which you are comfortable with. – Simon Sep 1 '13 at 17:55
  • Your question cannot be properly answered without an assesment of the threat vectors: how is your computer used (that includes setup and connections). – Jan Doggen Sep 3 '13 at 8:16
  • @JanDoggen lets talk about average/normal users, you see i didn't give enough details maybe, and maybe that's why it's voted down, but if i give too much details, my question will be closed because it will be too localized :) so lets just talk about average users – Lynob Sep 3 '13 at 10:04

Is it a bad idea to run more than one antivirus on the same PC?

Well, basically and technically, it depends on what these security applications do, how they behave in case they find a malware or a virus, or if they interfere with one another. If they don't effect each other's functionality you will be fine most of the time. To make matters clearer, there is a security solution named CORE Impact, which is not only the most expensive security package out there, but also must be mainly used by super paranoid, super advanced, or huge companies. When you want to install this application, many antivirus applications do not let it install accurately, that's why the installation progress asks you to uninstall all the other antivirus applications on your system. I myself do somewhat similar, like what you do, with a slight difference. I download a file and scan it using VirusTotal.com.

How far should one go to secure his PC? Where is the line between security and being paranoid?

I can not emphasize how much I hate it when you ask a security question and someone throwing the adjective "paranoid" at you, or simply attaching it to your name. I think that those who are mistakenly being called "paranoid", actually have a better cognitive ability than the rest. They sense that there is something wrong with Windows, and the moment they switch to something like Ubuntu or Fedora, they don't feel unsecured (that's what happened to me). Windows actually has a glorious reputation for its conspiracy theory and security backdoors and such, with its NSA Backdoor story being the top of the pyramid (just search google for these terms: "windows nsa backdoor" (without quotes of course) to see what is goig on). If you want ultimate security, you have got to move on from your disfunctional relationship with Windows and Microsoft. How far should one go to be secure? Well to be 100% honest with you: If you want to be 100% "secure" unplug your system from the Internet right now, do not install anything on it. Especially EXE files. There are many applications out there that all antivirus softwares recognize them as pure innocent heavenous applications, but they can and they are working for some governmental agency or a third party group or society that no one even knows that they exist. How far should you go? Well, this road doesn't have an end, and further you go ahead, rougher it gets. And I don't mean to scare you (ignoring the fact that truth almost always scares people).

Is trusting one Antivirus a good idea? I use two of the most well known antivirus, can't trust any.

Neither can I.

  • I know about NSA, and i dualboot my pc, using crunchbang linux most of the times, but there are things you cant do on linux, like running corona to develop mobile games, so i spend a lot of times on windows unfortunately – Lynob Sep 1 '13 at 18:49

I did said that you should search before writing up a question...

Since I'm answering (instead of commenting) I have a little more freedom in writing. So, analyzing your questions:

1. Is it a bad idea to run more than one antivirus on the same PC?

It is. No antivirus suite knows about each other running at background. So, your system will have an excessive overburden. Consider the following: you have two antivirus running full scans on your computer. What accesses what? And when? And how? Since two programs are doing intensive CPU and I/O processing, your system performance will plummet.

Besides that, most antivirus suites (giving AVG as an example) have some sort of a Resident Shield, that before any program running tries to quickly scan the file for potential hazards. Now if you have two antivirus suites, how are they going to deal that? Should suite A give priority to suite B, should the opposite happen, or should both try to open the file at the same time?

Probably the last on will be the one that happens most. Since no antivirus did read the file fully, they couldn't detect any hazard.

To sum up: Two or more antivirus suites = Less performance, more resource consumption, less security.

2. How far should one go to secure his PC? Where is the line between security and being paranoid?

I refer you to this question. Securing a new computer/laptop? [closed].

Essentially you can do what @terdon said and lock your computer behind a concrete bunker, never connected to power. And again I say, there is a lot of info about security in SU, just need to look it up.

3. Is trusting one Antivirus a good idea? I use two of the most well known antivirus, can't trust any.

Like I said on 1. having two antivirus suites is wrong, so, your experience is tainted by the fact you haven't left them running as they should: as only one running. So, try to uninstall one and see if you trust it, if not change.

You did said they detected different amounts of harmful data. Now, most modern antivirus suites use something called holistic detection. Has you might have figured out, no antivirus has copies of actual virus in their databases. They instead resort to certain behavioral rules that allow first to analyze an executable, figure what they want to do or how they were made and then determine if they are harmful. This leads however to the existence of false positives, that is, programs that, at the eyes of the scanner, seem harmful but are not, maybe because they were packed or compiled in ways the scanner doesn't know.

Now, you shouldn't trust on having a single protection. On my PC I have AVG as an antivirus suite, Malwarebytes as a malware scanner and Spybot as a spyware scanner. Since only AVG runs constantly (although Spybot has TeaTimer, that also runs on background), none of the other applications interferes with AVG detection.

  • I was just like you running only avg internet security for like 3 years or more, then i suspected that avg isn't protecting me as it should and i was right MWB detected too many viruses that avg did not, and i tried many antivirus before avg, norton, nod32, bitdefender, you name it, as for cpu, i don't run 2 scans at the same time, and MWB does not scan programs unless you told him to, so I'm not facing the problems you described about running 2 antivirus – Lynob Sep 1 '13 at 17:16
  • Like I said, there are a lot of things that differ between different antivirus suites. But now that I notice... Malwarebytes Pro isn't an antivirus suite - it's a malware scanner. So, actually, you had only a single antivirus suite. And AVG isn't the best malware scanner. – Doktoro Reichard Sep 1 '13 at 17:21

I was like you when I first bought my PC. Windows 7 is more secure than windows xp, so most executables won't run without your permission. I must say running two antivirus softwares is a bad idea which effects performance & leads to software conflicts which is worse. So stick to one Antivirus software.

If you want to choose a free antivirus software Avast is best & of course a firewall is important too. I would recommend Zone Alarm Free Firewall which is the best of the best. You can avoid malicious attacks by using site reputation add-ons on your browser.


i think 2 is really too much, passing over the slowness caused by two, i've had 1 free antivirus (avast), for a really long time, and nothing happened at all, the important is to keep it up to date, because if you aren't the target of an hacker, 2 antivirus are really too much

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