FileRepMalware :
It blocks files downloads if these conditions are *all* met:
1. The file is not prevalent enough, ie. not enough Avast users tried to launch the file yet,
2. The file is not signed or Avast does not trust the signature.
3. The file was not added to our cleanset.
For DomainRepMalware there is also this :
4. The domain is not prevalent enough, ie. not enough Avast users tried to download (any) files from the domain yet,