BouncyCastle.Crypto.dll is missing after MSI setup when Windows Defender is active

[florian-berger]

Hello,

I am using the NuGet package BouncyCastle (Version 1.8.6.1) in my project. For installing my software, I am providing a MSI installer created with WiX toolset.

When installing the software when Windows Defender Real-time protection is disabled, the library is copied correctly to the installation directory located in a subfolder in "C:\Program Files". When the installation path is excluded by rule, the file is also copied correctly. But when Windows Defender is active without exclusion, the file is missing after installing the msi.

When checking the DLL manually with Defender and on virustotal.com, no threat is detected. Have you ever heard of this behavior?

[florian-berger]

The problem still occurs. But I noted, that it is only happening when using Windows Server 2019 - on Server 2016, the Windows Defender doesn't block the file. In the Defender's log, nothing is logged.