Wacatac.B!ml isn't the name of any specific malware, it's just Microsoft's machine learning found something suspicious. "!ml" means machine learning, which refers to a program that Microsoft has that tries to learn which features of executables are common to malware and which aren't. The admin could submit it to Microsoft (filesubmission) and choose "not maleware" then none of you would ever get this false positive alarm.
Microsoft Defender is shit , DYOR and stop being uninformed.
