What is rundll32.exe?

by Gabriel E. Hall - -
rundll32.exe

Rundll32.exe is a legitimate Windows file used for DLL library distribution within system memory, although its name is also used by scammers

Rundll32.exe is a legitimate file which runs in the background of all Windows-based operating systems and is located in the \Windows\System32 folder. The process is a vital part of the OS – it helps with dynamic link library[1] (.dll) distribution within the memory. In other words, Dynamic Link Libraries are essential files that store parts of data that belongs to a particular application and cannot launch without the help of Rundll32.exe.

For that reason, Rundll32.exe rarely causes any problems, although some users noticed an unusually high CPU usage used by the process, or several instances of it running. Although rare, these unusual symptoms might indicate malware infection that can replace, corrupt, or mimic the original Rundll32.exe process. These malicious versions of the file might infiltrate other viruses into the device, include it into a botnet[2] and harvest users' sensitive banking details and use them for illegal purposes.

Additionally, the process name is known to be abused by technical support scammers[3] that insert malicious messages into Google Chrome, Safari, Mozilla Firefox, Internet Explorer, or another browser with the help of adware or redirect viruses. Thus, if you notice any type of “warning” message using Rundll32.exe process within a browser – it is a scam, and you should never call the provided number, or you might lose a lot of money.

Name rundll32.exe
Developer Microsoft
Runs in Task manager
Related to explorer.exe
Danger level The original file is not dangerous, although malicious versions can pose a tremendous risk for users' privacy
Malicious or legitimate? To make sure that Rundll32 is safe, run a scan using Reimage or another security software

The initial Rundll32.exe should rarely cause any troubles, although, just like any other executable, it can cause certain errors. In such a case, there is a chance that the related .dll file is broken, or there is something wrong with system files altogether. If you encounter any type of Rundll32.exe errors, you should run a System File Checker or employ Reimage – it can fix Windows-related errors automatically.

However, if you have noticed multiple Rundll32.exe processes within Windows Task Manager or high resource usage by the process, it might indicate a malware infection. The rundll32.exe file is often a target of hackers who seek to hide severe computer infections like spyware, keyloggers, Trojans, and other behind it. To make sure that is (not) the case, please run a full system scan using reputable anti-malware software.

In another case, you might encounter the “Error code: rundll32.exe” fake error that shows up within the browser during web browsing sessions. There are multiple different versions of the scam, but one of the examples reads as follows:

Confirm Navigation

The problem is caused by an unusual activity performed on this machine. Error code: rundll32.exe. Call Microsoft Support Number Now – +1-844-988-6363 and share this code with the agent.

Are you sure you want to leave this page?

Without a doubt, legitimate scanners require to be stand-alone applications, and claims about malware infection, system corruption or other issues within browsers are utterly bogus. Never call the provided number, as crooks might talk you into giving them permission to access the computer remotely and install malware, or make you pay for bogus tech support.

While adware might display false undll32.exe virus alerts, it can also show other different symptoms, such as:

  • Excessive amount of intrusive ads;
  • Irritating interstitial ads;[4]
  • Browser slowdown;
  • Redirects to unknown / suspicious websites;
  • System freezes, etc.

The legitimate rundll32.exe file is typically located in the folder C:\Windows\System32. If you suspect that virus or malware might have corrupted the file, check the location of the file. If it's not located in the System32 folder, then you should remove rundll32.exe file immediately. For this purpose, use a reliable anti-virus with updated definitions. Otherwise, it can start downloading malware onto your PC.

Main techniques used to spread malware

Most of the legitimate Windows OS files are built in by default and cannot download as standalone installers. In case of corruption, such system's components are normally fixed by installing the latest updates or using professional systems' optimization tools.

However, malware that pretends to be one of the system's files can sneak into the system in various ways. One of the primary malware distribution technique is freeware bundling. For monetization purposes, freeware developers supplement their products with multiple browser extensions, add-ons, and toolbars, which travel marked as default components. Consequently, if the user ends up selecting Quick installation method, he or she agrees with the installation of the whole package. To prevent adware and browser hijacker on the system, it's a must to select Advanced setup all the time and deselect unwanted components.

More severe computer infections are usually disseminated via exploit kits, malicious spam email attachments, infected links, fake or phishing websites, phony update prompts, illegal software installed, and so on. Although there's no hundred percent protection from severe computer infections, keeping the system updated and establishing a professional anti-malware tool is usually sufficient to deter infections.

A comprehensive Rundll32.exe virus removal tutorial

The original Rundll32.exe should not be terminated or otherwise modified. Rundll32.exe removal can cause severe system malfunctions or even crash. However, if you suspect that this file has been compromised, you should scan the system with anti-malware. There's no way to remove the Rundll32.exe virus manually.

The first sign of Rundll32.exe error is an increase CPU usage. Besides, multiple processes of this file should be running within Task Manager, none of which can be terminated. Finally, general system's slowdowns, crashes, and freezes are also common symptoms of Rundll32.exe malware.

If you are constantly encountering “Error code: rundll32.exe” scam, you can find a comprehensive adware removal guide here.

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What to do if failed?
If you failed to remove virus damage using Reimage, submit a question to our support team and provide as much details as possible.
Reimage is a recommended tool to scan your system for possible threats and crappy software. The trial version of the product will find harmful applications in your system.
Alternative Software
Different security software includes different virus database. If you didn’t succeed in finding malware with Reimage, try running alternative scan with SpyHunter.
Alternative Software
Different security software includes different virus database. If you didn’t succeed in finding malware with Reimage, try running alternative scan with Combo Cleaner.

About the author

Gabriel E. Hall
Gabriel E. Hall - Passionate web researcher

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