Avast missed malware on the flash drive but not on download.

Avast Free Antivirus / Premium Security
1

I scanned my friend’s flash drive and it missed coiubx.exe. I tried googling it and found a website having a copy of the malware. I tried to download it. When it is almost done, avast catches it, and I sent it to the virus chest.

It is found here
hxxp://www.zidofile.com/oiXHAD (It is a Thai website)

I wonder why the file is not caught while scanning the flash drive, but downloading it from the web it is caught.

Is there a separate virus database for the network shield and filesystem shield?

2

upload the file(s) to www.virustotal.com and test it with 43 malware scanners
when you have the result, copy the URL in the address bar and post it here

3

Hello,
and is it the same file for sure? Same content inside? Not only same filename? Send us (virus@avast.com) both files to analyze, please.

Milos