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Should I remove cnmnsst.exe and how?

  1. Oct 16, 2013 #1
    I notice when I am on the web, the pointer is slow and the fan comes on. I check and I found cnmnsst.exe running and take up a lot of memory. It is part of the Canon stuff, but I don't use my Canon printer when I surf the web. Should I remove and how?

    I found sites that can remove this, but I don't trust using those in my computer, anyone has a trusted site that can do this?


  2. jcsd
  3. Oct 16, 2013 #2

    jim mcnamara

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    Something else is wrong. Either cnmnsst is not what you think ( try check summing the file, then go to http://www.processlibrary.com and check). Or some other process is doing something it should not. See here to learn how to download the microsoft FCIV tool:


    Just because something is named foo.exe does not mean that it is the REAL foo.exe. A lot of malware hides inside known good executables.

    You do have active malware and virus protection? Please say 'yes' ....
  4. Oct 16, 2013 #3
    Thanks, I have Norton from day one of this computer and I have MS security suit on also.

    What can check sum tell me. How do I run the check sum?

    I did program search, it is from the program of my Canon scanner. But I don't understand why it is running. I am not using the Canon at the moment.
    Last edited: Oct 16, 2013
  5. Oct 16, 2013 #4
    If you mean you have a virus scanner from Norton installed and a virus scanner from Microsoft installed I suggest you pick one and remove the other. Having two installed on your computer is pointless. As a computer professional my suggestion is Microsoft Security Essentials for the best cost/benefit ratio.

    Check sum will tell you if the cnmnsst.exe you have is exactly the same as the one Canon provided. If the checksum of the file you have isn't exactly the same as the one found at http://www.processadvisory.com/process/cnmnsst-exe [Broken] then something has modified yours and given your other symptoms it's probably malware. Further investigation should be taken, preferably in safe mode and disconnected from the internet.

    When comparing checksum values be sure you're looking at the correct version. The value is different for every version of the file.

    You can get a utility that will tell you the checksum of any file on your computer here: http://sourceforge.net/projects/checksumwindows
    Last edited by a moderator: May 6, 2017
  6. Oct 16, 2013 #5
    Thanks for the info, it is a little over my head, I have to spend a little time to try all these and report back.

  7. Oct 16, 2013 #6


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    I just fixed a friends computer that had a lot of junk running and he had a very small amount of RAM which together, caused his computer to run very slow. Many programs like this one will run constantly so that they can "check for updates". It's usually safe to go into your services and set it to manual startup mode so that they only start when you open that program. Also, do just like the link states and create a restore point first.

    Here's a link for working with your services that explains the services in detail - just remember, with great power, comes great responsibility. Be very careful with service settings. You can really screw up your computer if you shut off the wrong things. Also, be sure to set a restore point before making any changes.
  8. Oct 19, 2013 #7


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    Are you saying that when this happens the Canon driver is using a LOT OF CPU. It doesn't matter if it is using memory unless it is causing a lot of swapping.

    If so, I'd start with uninstalling the Canon driver and downloading and installing the latest.

    If that didn't fix it I'd start messing with the scanner. Turn it off, see if it stops using CPU. Turn it back on, see what might be causing it to use CPU. Scan a document, see if that starts or ends it, etc.

    Follow the instructions at the Canon site for updating the driver. If you can't figure it out, post your OS information and Model number of the scanner.

    You may be able to bring up the scanner application and check for updates, or for Windows, uninstall it through the control panel. Otherwise you need to do it in the device manager.
  9. Oct 30, 2013 #8


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    Definitely do not use Microsoft Defender AND a commercial anti-virus at the same time. If your computer is running slow, I would uninstall the commercial anti-virus (and use Defender instead).
  10. Oct 30, 2013 #9


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    Personally I would disable windows defender. Based on AV effectiveness testing, it doesn't do too well except in the false positives category. (My unattended computer got infected by an ad server exploit on a news site webpage while Defender was running - Microsoft's response was ---- sorry but we don't protect against that).

    I assume the OP is long gone, BTW
  11. Oct 31, 2013 #10


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    Except that, here, the problem is an overwhelmed/slowed-down machine. The commercial anti-virus is more likely to cause that, whereas Windows Defender should not.
  12. Oct 31, 2013 #11


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    Except they are rated below Symantic in performance. And they often totally peg the disk drive for up to 5 minutes --- especially after an update (well, they did for me, anyway). They are better than they used to be, but far from good.

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