Copy file from outside the projected filesystem

[Eznopot]

I have developed a program using ProjFS to synchronize files between my backend and a Windows session. Everything works as expected within the projected filesystem: I can create, modify, delete, copy, and move files.

However, when I try to copy a file from outside the projected filesystem into it, Explorer.exe gets stuck during the copy process. I don’t receive any errors or logs from ProjFS, which makes it difficult to debug the issue.

Has anyone encountered this problem before or have suggestions on how to resolve it? I can share specific parts of the code if needed.

Thank you in advance for your help!

[Eznopot]

Hello,

I continued investigating the issue, and I found that the problem is caused by Microsoft Defender. During the file copy process, Defender performs a checksum (specifically, opening the file with ifstream), which blocks the file opening operation. As a result, my program was stuck on the following line:
std::ifstream file(filePath, std::ios::binary);

To temporarily address the issue, I started by whitelisting my program's executable in Microsoft Defender. While this approach works, it is not feasible for production in the context of my project.

Instead, I added the following logic in my program during the OPEN event notification to prevent the antivirus from accessing the file:

if (CallbackData->TriggeringProcessImageFileName) {  
    if (EndsWithStringI(CallbackData->TriggeringProcessImageFileName, L"MsMpEng.exe")) {  
        return;  
    }  
}

Although this fix works, it is not ideal or recommended. Does anyone have a better solution for handling this situation?

Thank you in advance for your insights!