Hi, The Malicious Software Removal Tool does not use an installer. Typically, when you run the Malicious Software Removal Tool, it creates a randomly named temporary directory on the root drive of the computer. This directory contains several files, and it includes the Mrtstub.exe file. Most of the time, this folder is automatically deleted after the tool finishes running or after the next time that you start the computer. However, this folder may not always be automatically deleted. In these cases, you can manually delete this folder, and this has no adverse effect on the computer. Meanwhile, the main mrt.exe file will be updated after the new version is released once a month. Hope the information is helpful. Best Regards, NikiPlease remember to click "Mark as Answer" on the post that helps you, and to click "Unmark as Answer" if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.

Hi Niki, Thank you very much for your input, but that's not what I wanted to know. I know it's not listed in the registry as an installed update. I'm asking if I can remove the executable from that location (%SystemDrive%\(alphanumeric string)\mrtstub.exe) since, as you just confirmed, it only runs once after each update. And I was asking if deleting it would be a problem in the next MRT update or if Windows Update would just put a new copy there. I'm asking this because I don't know if Microsoft updates mrtstub.exe monthly or just the main mrt.exe in system32. If that's the case and both of them are updated at the same time, it wouldn't be a problem if I removed mrtstub.exe (or even mrt.exe for that matter), since they would be downloaded again. I hope I've made myself clear now. And once again, thanks a lot for your help.

Hi, The Malicious Software Removal Tool does not use an installer. Typically, when you run the Malicious Software Removal Tool, it creates a randomly named temporary directory on the root drive of the computer. This directory contains several files, and it includes the Mrtstub.exe file. Most of the time, this folder is automatically deleted after the tool finishes running or after the next time that you start the computer. However, this folder may not always be automatically deleted. In these cases, you can manually delete this folder, and this has no adverse effect on the computer. Meanwhile, the main mrt.exe file will be updated after the new version is released once a month. Hope the information is helpful. Best Regards, NikiPlease remember to click "Mark as Answer" on the post that helps you, and to click "Unmark as Answer" if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.

Hello there, My question is quite simple. Can I safely remove the Malicious Software Removal Tool Update Stub from my local disk? Is it run more than once after update? Will it interfere with the next MRT update or just download normally? Location is %SystemDrive%\(alphanumeric string)\mrtstub.exe Thanks

Hi, I would like you to know Malicious Software Removal Tool Update Stub cannot be uninstalled from your local disk. It is not listed in Control Panel\Programs\Programs and Features\Installed Updates. Microsoft releases an updated version of this tool on the second Tuesday of each month. The version of the tool delivered by Microsoft Update and Windows Update runs in the background and then reports if a malware infection is found. It just runs once after the new version is downloaded. It is to say it runs once a month. If you want to run that tool more than once, you can download it from the following site manually. http://www.microsoft.com/security/pc-security/malware-removal.aspx Best Regards, NikiPlease remember to click "Mark as Answer" on the post that helps you, and to click "Unmark as Answer" if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.