Always happens with unofficial builds. Windows 10 build 9901 surfaced a few days back, and users rushed to give it a try, even though Microsoft maintains that sticking to official build is the way to go.
It so happened that a number of antivirus solutions have begun flagging the leaked build as malware.
Take a look at this scan results, for instance, which mark the C:\Windows\SysWOW64\Wpc.dll file included in this version of the operating system as infected. No wonder then that some people directly asked Microsoft officials regarding this.
Luckily, the helping hand of Gabriel Aul is here to, well, help.
In a short tweet the head of the Windows Insider program confirmed that this is just a false positive, and there is no need to worry about build 9901 being affected with any sort of malware.
@jessenic Yes, we confirmed this looks like a false positive.
— Gabriel Aul (@GabeAul) December 16, 2014
So why the flag, you ask?
Chances are that this build comes with some changes which put out the antivirus engines on these security software. The associated companies will surely update their programs in the near future, seeing as this very clearly is a false positive.
Redmond still does not recommend the installation of this leaked build, though, meaning sticking to the official builds is still the best choice for the time being.