How to remove the calc virus

Most antivirus programs identify calc.dll as malware—e.g. Symantec identifies it as Infostealer or Trojan Horse, and Microsoft identifies it as VirTool:Win32/Obfuscator.HG or Trojan:Win32/Opachki.A.

The free file information forum can help you find out how to remove it. If you have additional information about this file, please leave a comment or a suggestion for other users.

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Calc.dll file information

The process known as Application appears to belong to software Microsoft by Microsoft (

Description: Calc.dll is not essential for Windows and will often cause problems. The file calc.dll is located in the C:\Windows\System32 folder. Known file sizes on Windows 10/8/7/XP are 24,064 bytes (33% of all occurrences), 23,552 bytes, 25,088 bytes, 26,112 bytes or 25,600 bytes. 
A .dll file (Dynamic Link Library) is a special type of Windows program containing functions that other programs can call. This .dll file can be injected to all running processes and can change or manipulate their behavior. The process is loaded during the Windows boot process (see Registry key: MACHINE\Run). File is hidden. The file is not a Windows core file. The program has no visible window. The service has no detailed description. It can change the behavior of other programs or manipulate other programs. Calc.dll is able to manipulate other programs. Therefore the technical security rating is 90% dangerous, however you should also read the user reviews.

Recommended: Identify calc.dll related errors

Important: You should check the calc.dll process on your PC to see if it is a threat. We recommend Security Task Manager for verifying your computer's security. This was one of the Top Download Picks of The Washington Post and PC World.


User Comments

Part of Opachki.a Trojan
  Ken   (further information)

Summary: Average user rating of calc.dll: based on 1 vote with 1 user comment. One user thinks calc.dll is dangerous and recommends removing it.

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Best practices for resolving calc issues

The following programs have also been shown useful for a deeper analysis: ASecurity Task Manager examines the active calc process on your computer and clearly tells you what it is doing. Malwarebytes' well-known Banti-malware tool tells you if the calc.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.

Should you experience an actual problem, try to recall the last thing you did, or the last thing you installed before the problem appeared for the first time. Use the 6resmon command to identify the processes that are causing your problem. Even for serious problems, rather than reinstalling Windows, you are better off repairing of your installation or, for Windows 8 and later versions, executing the 7DISM.exe /Online /Cleanup-image /Restorehealth command. This allows you to repair the operating system without losing data.

Other processes

calc.dll [all]