there is an official reply about this issue on bminer website:
https://www.bminer.me/faq/#why-does-windows-defender-report-bminer-as-virus-malicious-softwareBminer uses DRM techniques to prevent itself to be tampered. Anti-virus softwares sometimes classify them as viruses because the techniques are used to obfuscate malicious software.
Bminer is not a piece of malicious software. You do have to add an exception in Windows Defender to use it. However, we strongly recommend to check the hash signatures when you download the releases to ensure the software has not been tampered.