Sorry but no AV is 100% you can send undetected files to avast via email.Submit to submit@virus.avast.com

Also avast does detect USB viruses as well it has saved me couple a times from it.Sometimes some these samples are polymorphic meaning they change constantly so it get harder to detect that’s why avast had behaviour shield and deepscreen to help detect unknown malware if it is executed. :slight_smile:

Also you can PM me the download link.I will check the samples and upload it personally.

Are you using the latest avast free? It has major improvements over the older ones.