Stmain.dll is a browser extension for Internet Explorer. This add-on enables several additional functions for Internet Explorer. You can disable it through the Extras menu (key combination Alt + X) under Manage Add-ons. The following paragraph provides more information about MSN Search Toolbar.
Description: Stmain.dll is not essential for Windows and will often cause problems. Stmain.dll is located in a subfolder of "C:\Program Files"—generally C:\Program Files\MSN Apps\ST\01.02.3000.1002\en-xu\.
Known file sizes on Windows 10/8/7/XP are 155,648 bytes (99% of all occurrences), 143,360 bytes or 141,824 bytes.
This .dll file is a Browser Helper Object (BHO) that runs automatically every time you start your web browser. BHOs are not stopped by personal firewalls, because they are identified by the firewall as part of the browser itself. BHOs are often used by adware and spyware. IDs used by this BHO include 9394EDE7-C8B5-483E-8773-474BF36AF6E4. The program has no visible window. The stmain.dll file is able to monitor web browsers. There is no detailed description of this service. Stmain.dll is not a Windows system file. There is no information about the author of the file. Stmain.dll is able to record keyboard and mouse inputs. Therefore the technical security rating is 76% dangerous, however you should also read the user reviews.
Recommended: Identify stmain.dll related errors
External information from Tony Klein:
Important: Some malware camouflages itself as stmain.dll. Therefore, you should check the stmain.dll process on your PC to see if it is a threat. If MSN Search Toolbar has changed your browser's search engine and start page, you can recover your browser's default settings as follows:Reset default browser settings for Internet-Explorer ▾
The following programs have also been shown useful for a deeper analysis: ASecurity Task Manager examines the active stmain process on your computer and clearly tells you what it is doing. Malwarebytes' well-known Banti-malware tool tells you if the stmain.dll on your computer displays annoying ads, slowing it down. This type of unwanted adware program is not considered by some antivirus software to be a virus and is therefore not marked for cleanup.
A clean and tidy computer is the key requirement for avoiding PC trouble. This means running a scan for malware, cleaning your hard drive using 1cleanmgr and 2sfc /scannow, 3uninstalling programs that you no longer need, checking for Autostart programs (using 4msconfig) and enabling Windows' 5Automatic Update. Always remember to perform periodic backups, or at least to set restore points.