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AVAST instup.dll detected as a Trojan.Dropper


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Wow, that is a very old version of Malwarebytes. Not even supported at this point, but let's see if we can get it to work @JimA1

Malwarebytes Anti-Malware version

The last version of the 1.x series was 1.75 and it was end of life on June 8, 2017
The 1.7 version you have was end of life support on April 9, 2015





Please disable Avast real-time protection

Then with protection disabled open Malwarebytes and see if you can now restore the file or not and let me know.


If that does not work then you can download the installer and reinstall Avast


Edited by AdvancedSetup
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Just thought I'd chime in here...

If you have that file (instup.dll) multiple times in the quarantine list of Malwarebytes, then presumably Avast kept recreating or redeploying that file on your computer and Malwarebytes kept quarantining it, right?  At least that appears to be what happened on my end.  Are you sure that file isn't once again back in the appropriate location (in which case there is no need to remove an older copy of it from quarantine)?

And if not, you could always just try uninstalling and reinstalling Avast - that would probably be the easier first step.  

Either way, if you get the instup.dll file back in place and Avast works again, you can probably just ignore whatever has been previously quarantined by Malwarebytes - although others can advise if this is completely correct or not, although I don't see any reason why it wouldn't be...

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AdvancedSetup and mbressman, thanks for your responses and suggestions.  It looks like the problem is fixed and the Avast virus protection can again update.  Here is what happened:

Per AdvancedSetup’s suggestion, I temporarily disabled Avast’s real-time protection and then attempted to remove instup.dll from Malwarebytes’ quarantine.  Was still unable to remove the file from quarantine.

I went to the link AdvanccdSetup provided and downloaded an Avast installer file using one of the links from the web page.  I ran the installer file without first uninstalling Avast, which I was reluctant to do unless necessary.  When I launched the Avast installer file, right away Malwarebytes quarantined it.

I then went to the Avast web site and downloaded an installer file directly from Avast.  It didn’t look promising when I saw that the file name was exactly the same as the first one I downloaded that Malwarebytes quarantined, but this one ran.  Shortly it displayed a message that it couldn’t work because the file instup.dll was missing, but it continued to run.  When it finished, from all appearances the updated Avast software was present with updated virus definitions.  The file instup.dll is back where it should be and from what I can see to this point, everything is working now.

mbressman, I think you are correct about the reason I was seeing multiple instances of the instup.dll file in the Malwarebytes quarantine.  After attempting to remove it from quarantine I wasn’t seeing it back where it belonged and Avast continued to say it couldn’t update.  I still wonder why I wasn’t able to remove the file from the Malwarebytes quarantine.  I think you are also correct about not needing to be concerned about the file continuing to display in the quarantine list after the Avast install ran and put the file back in place, since Avast now seems to be working since that was done.

Again, thanks to you both for your help.  AdvancedSetup, my compliments to you as well for the detailed instructions you gave on what to do and how to do it, including the links you provided to what you were suggesting for me.

Best regards,


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I would  also recommend creating exclusions between Malwarebytes and Your AV to help prevent any possible conflicts or performance issues.  Please add the items listed in this support article to Your AV 's allow list(s)/trust list(s)/exclusion list(s) particularly for any of its real-time protection components and likewise add Your AV 's program folder(s) (likely located under C:\Program Files and/or C:\Program Files (x86)) to Malwarebytes' Allow List using the method described under the Allow a file or folder section of this support article and do the same for its primary data folder which is likely located under C:\ProgramData (you may need to show hidden files and folders to see it).

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