Most antivirus programs identify WinDef.exe as malware—for example Kaspersky identifies it as Worm.Win32.VBNA.b or not-a-virus:RiskTool.Win32.BitCoinMiner.ccx, and BitDefender identifies it as Gen:Variant.Kazy.152275.
The WinDef.exe file is a software component of N/A - Virus.
“windef.exe” is a malicious file in Windows that is part of several viruses, obtained by way of mass-mailing campaigns, browser helper objects, etc. Upon installation/activation of certain viruses, this file is created and added into the registry and startup list. It usually receives fake properties information that represents Microsoft and Windows Defender, which is not related. Defender is often referenced as WinDef, but does not contain an executable with the same name. “windef.exe” can appear in places like [User\Application Data], [Program Files], [Program Files (x86)], etc. and is used in many different ways, including to steal personal information, logins, bank account numbers, etc. or simply be used to create annoying pop-ups, as well as spy on the user’s browsing activity or keystrokes. Viruses like Win32/Vercuser, obtained from removable media, install it with several other files and open the door to more virus installations. The virus known as "Wolfteeth Bot Catcher" also installs it with other files and uses it to transfer the backdoor Trojan named bycnboy.exe.
WinDef stands for Windows Defender
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Description: WinDef.exe is not essential for Windows and will often cause problems. WinDef.exe is located in a subfolder of the user's profile folder.
Known file sizes on Windows 10/8/7/XP are 352,256 bytes (33% of all occurrences), 62,976 bytes or 13,179,660 bytes.
There is no description of the program. The program has no visible window. The file is not a Windows core file. The software starts when Windows starts (see Registry key: MACHINE\Run, Run). WinDef.exe is able to record keyboard and mouse inputs and monitor applications. Therefore the technical security rating is 67% dangerous.
Recommended: Identify WinDef.exe related errors
If WinDef.exe is located in a subfolder of "C:\Program Files", the security rating is 56% dangerous. The file size is 3,003,628 bytes. The process has no file description. The program is not visible. It is not a Windows system file.
Important: You should check the WinDef.exe 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.
The following programs have also been shown useful for a deeper analysis: Security Task Manager examines the active WinDef process on your computer and clearly tells you what it is doing. Malwarebytes' well-known anti-malware tool tells you if the WinDef.exe 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 cleanmgr and sfc /scannow, uninstalling programs that you no longer need, checking for Autostart programs (using msconfig) and enabling Windows' Automatic 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 resmon 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 DISM.exe /Online /Cleanup-image /Restorehealth command. This allows you to repair the operating system without losing data.