What is rundll32.exe and why is it running on my Windows PC?

By ivan.diskin | May 24, 2018 |

greater than 10 minutes

It is not a stretch to say you ended up here because you somehow discovered the Rundll32.exe process and started wondering what it was. We are glad to tell you that you are at the right place. Here, you would get answers to the following questions and much more:

  • What is Rundll32.exe in Windows 10 and older Microsoft operating systems?
  • Why is the Rundll32.exe process always running?
  • Why does it use up so much system resources?
  • Is it safe to disable Rundll32.exe?
  • Can I delete this strange file?
  • Is it a threat to my PC?  

We would like to assume that you are familiar with the presence of DLL files (items that have the .dll extension) on Windows. These files consist of pieces of application instructions or logic, and several programs access their data efficiently through this setup. DLL is short for Dynamic Link Library. Unlike Rundll32.exe, btmshellex.dll is an example of such a file.

As far as we know, there is no direct way of launching DLL files. After all, they are not applications in the perceived sense—they cannot work on their own. Microsoft did not design such items to run on programs like images open in the Photos app, for example.

The Rundll.32.exe is an essential component of the setup that Windows employs to use the functionality in shared .dll files. In simpler words, it assists other programs that have DLL files to run as their developers intended them to work.

When an application on Windows needs to use a DLL file, Rundll32.exe springs into action. These operations usually occur in the background without bothering you. It is doubtful that you (the user) would ever have to run the Rundll32.exe file or similar items.

It is time you understood that Rundll.32.exe lives a simple life in the Windows operating system environment. There is almost always at least one copy of this item running at any given time. The file or process is usually at this location: Windows \ System32 \ rundll32.exe. Or it is supposed to be, at least. The official Rundll32.exe file from Microsoft is harmless. It would never cause trouble on Windows.

Sometimes, viruses or other malicious programs try to disguise themselves as this file to avoid detection. In such scenarios, if you carefully try to find out the actual location of the suspicious Rundll.32.exe process, you might realize that this item in a directory that differs from the stated position above. Such happenings are worrisome.

How to disable the Rundll32.exe process?

We advise that users do not disable Rundll32.exe except in cases where the measure is vital. You must not mess about with this particular process. In fact, any unauthorized removal of this file would result in a severe malfunction of your computer or even a critical Windows crash.

In the scenarios where you have your hands tied, you must open the System Configuration app and continue from there. Follow these instructions:

For users running Windows 7:

  • Press (and hold) the Windows button on your keyboard, then tap the letter R key to launch the Run app. After the small window opens, type msconfig into the available text box and hit the Enter key to run the code you just inputted. The System Configuration app should open now
  • Navigate to the Startup tab. There, you should see the startup items (processes or executable files). Locate the Rundll32.exe file or any program associated with it and untick the corresponding checkbox to prevent Windows from starting it when your computer boots up.

For users running Windows 8, Windows 8.1, and Windows 10:

  • You can disable the Rundll32.exe process through the Startup menu in the Task Manager program: press (and hold) the CTRL and ALT button on your keyboard, then tap the Delete key to see a list of programs or options. From that menu, click on Task Manager to open the required app
  • After the Window opens, navigate to the Startup tab. Find the Rundll32.exe process or the file associated with it. Right-click on the item in view and select Disable

This operation might be a lot more difficult than it should be if you failed to locate the Rundll32.exe file. You will also struggle to identify the object if it is not associated with a startup item. You would have to dig deep to find the source of the process. Some system research is in order here.

How to verify the genuineness of the Rundll32.exe file:

For users using the Task Manager program on Windows 7 and more recent iterations of Microsoft’s operating system, you have the option of seeing the full command line for all applications that are currently on your computer. You can take advantage of the feature to check if the Rundll32.exe you are seeing is the real deal. Here are the instructions you need on carrying out the necessary operations:

  • First, you must open the Task Manager application (we provided instructions on doing this earlier). After the required window loads, navigate to the Processes tab. Windows 10 users should go to the Details tab
  • You should see the list of processes that Windows is running currently. Locate the Rundll32.exe file. You might see multiple files with this name. No need to panic
  • Go to Views or Select Column. In your current location, you should see the option for Command Line. Tick its check box to select it
  • Windows should now show you the full path for the items on the list. If it does not, right-click on the object in view and select Open File location from the options that come up. A window showing a particular directory in the File Explorer program should show up now
  • Go through the presented information and take note of anything suspicious. Of course, you already know that the Rundll32.exe is supposed to be in the System32 directory. If it is not there, you might have reason to worry. You should also see the base DLL file in the same directory
  • To obtain more information about a specific file, hover your cursor around its text. You should see the following details: File description, Company, File version, Date created, and size
  • If you feel the presented data was not enough, you can open the Properties window for the file in view and find out even more about the item. There, you can navigate to the Details tab to know the purpose of the object. Regardless, you would surely find whatever it is that you are looking for under the remaining tabs: Digital signatures, Security, and Previous Versions

There is another way of identifying the programs that the Rundll32.exe component is assisting to run currently. This alternative method might be better for some users, especially those running the more recent versions of the Windows operating system (Windows 8.1 and later). Here are the instructions you need to follow:

  • Click on the Windows Start icon and input cmd into the available text box. From the search results that come up, you should see Command Prompt (Desktop app). Select this item from the list to open the needed program
  • After the window opens, type in the following code and hit the Enter button on your keyboard to run the command: tasklist /m /fi “imagename eq rundll32.exe”
  • If Windows carried out the operation successfully, you should see a list comprising of running services with some details about the presented items.

Remember to examine the names of all the items you found very carefully. We know of reports where users stated that they had luckily found a malicious DLL file that had almost escaped detection because its creators (attackers) had given it this name ” rundl132.exe”. Here, note that the number 1 is very similar to the letter l. Not everybody might notice this little detail at first sight.

How to solve problems associated with the Rundll32.exe file

We have compiled reports from users about issues associated with the Rundll32.exe file. If you are experiencing one of the following problems or can relate to any of the events below, then there is a good chance that your system is infected. Note that the list below is far from being an exhaustive one; there are many other symptoms of malware activity.

  •    You find a suspicious Rundll32.file, and you consider it a virus because the Task Manager program showed you multiple versions of it running at once. If the shady processes you identified are using up ridiculous amounts of your system resources, then your assumptions are even more likely to be correct
  •    You are experiencing a lot of unexplainable performance issues and system slowdowns
  •    Your browser applications like Chrome, Firefox, Internet Explorer and so on show this disturbing notification while you are on the web: Error code: Rundll32.exe
  •    The presence of an excessive amount of intrusive ads and pop-ups when you are browsing and even when you remain in the typical Windows computer environment
  •    Frequent redirects to fishy websites when you are trying to access a correct web address

Now, we would first explore solutions to the problems (involving Rundll32.exe) that came up naturally, and those that are results of accidental user operations. In theory, Windows is supposed to inform you if this file goes missing, suffers corruption, or if something damages it.

  •    If you accidentally deleted the Rundll32.exe file, then you must restore it to its original location from the Recycle Bin program. For your sake, we hope you have not disabled this Windows utility
  •    If your antivirus or antimalware application wrongly quarantined Rundll32.exe, you can quickly restore the lost item back to your computer by checking for it in your security program’s quarantine vault and using the Restore option there
  •    If the file got missing and you cannot figure how, why, or when it happened, then you must run the System File Checker tool to restore lost or corrupted files. You can also check your hard disk for errors and corruption, using the built-in Windows utility for such operations. Otherwise (if all else fails), you must use the System Restore program to go back in time.

If Windows showed you a Rundll32.exe file and you considered it suspicious because you could not understand its purpose, you might be tempted to disable it. We are against such a decision. To be fair, you should know that it is always better to do some research online to be sure that what you are about to do is the right thing.

If Windows led you to a directory in the File Explorer program and you realized that the destination is not the correct location for Rundll32.exe, then all is not as it seems. A malicious program might be working in disguise while using the name of that file to avoid detection.

We recommend you check for viruses, spyware, adware and other forms of malicious programs. Open your security program (antivirus, for example) and run a full (comprehensive) scan on all the directories and files paths on your computer.

How to resolve issues with Rundll32.exe?

If your main security app detected nothing or you feel that the program is struggling to do its job correctly, you should consider downloading and installing an excellent antimalware application like Auslogics Anti-Malware. Use this program to scan for threats to increase the chances of you finding the dangerous items on your system.

Auslogics Anti-Malware is a superb app that does a great job, and at the same time, it does not interfere with operations of your antivirus (regardless of what brand)—well, if your system is running one. The addition of an antimalware program to your security suite provides that significant extra layer of protection that helps to keep your PC as safe as possible.

If you eventually find a virus or malware on your PC after the scans, you should quarantine it. You can even get rid of it permanently. Sometimes, you might lose other essential items if your security app detects an entire folder as a threat.

If you do not have any security program installed on your computer, then you can at least attempt a straightforward procedure to find dangerous items masquerading as the Rundll32.exe file. You must never consider this process a substitute for the search for threats carried out by an antivirus or antimalware app. But, it is something at least. Here are instructions you are waiting for:

  • Click on the Windows Start icon (or press the Windows button on your keyboard) and search for “rundll32” without the quotes
  • Select the required item from the search results. The only legitimate version of the file should be in the following directory: C: \ Windows \ System32 \
  • You can also open the File Explorer program and navigate through the stated path to get to the needed directory. Now you must create a backup of that file in case anything goes wrong. Right-click on the object in the correct folder and select Copy from the list of options that come up
  • Store the copied file in a safe and accessible place. Your desktop, for example, is an excellent location. Paste the item there and rename it. The new title should be something you would have no problem remembering and at the same time, it must not differ too much from the original name of the item. For example, rundll32COPY.exe
  • Now return to the search results. You can perform the same operation once more if necessary. Whatever you do, take note of all the Rundll32.exe files that are not in the correct directory. Get rid of all of them. In fact, we advise that you empty your Recycle Bin to delete the removed items permanently
  • After you have finished eliminating all the threats and suspicious items, restart your PC to let the changes take full effect. We sincerely hope that you made no mistakes while trying to fix your issues. You should no longer experience problems if you got rid of all the harmful files and left only the legitimate one intact.

If you realize that you accidentally deleted the Rundll32.exe file, then you must restore it to its original location by using the backup you created earlier: copy it, place it in the required directory and change its name to back “Rundll32.exe”.

If you are unable to narrow down the infected files, then you must get rid of everything. However disappointing as this occurrence might be, we consider it a small price to pay if your safety is on the line.

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