DLL

• DLL, or Dynamic Linked Libraries, is a tool used by Windows developers to add features to their programs. The RunDLL32.exe program is the Windows operating system command that allows them to use the features provided by a DLL in their own programs.
  
  

Dangers

• Since RunDLL32.exe is such an important part of the Windows operating system, many virus, trojan and spyware programs attempt to impersonate the rundll32.exe program to evade detection. A valid Rundll32.exe program should be located in the folder C:\Windows\System32. If you believe there is a fake version of rundll32 running on your computer, you may need to purchase a quality antivirus program.
  
  

Impersonation Methods

• One trick used by viruses to impersonate the rundll32 program is to create a file that, on casual inspection, appears the same. For example, some viruses use names like "rundII32," replacing the lower case "L" with a similar looking capital "I."