Windows Defender suddenly detects files as Trojan:Win32/Bluteal.B!rfn. Microsoft confirms this is a false positive. This detection may have been resolved yesterday, June 26th, as it is listed in this update. Microsoft has not told what definition update pushed or when it was resolved. If you are still seeing this behavior, you should check for new updates for Windows Defender and install them. If new definitions are available, they will be listed as “Definition Update for the Windows Defender”””
Source: https://www.bleepingcomputer.com/news/security/windows-defender-detecting-legitimate-files-as-trojan-win32-blutealbrfn/