it might be a stupid question,can Avast scan Brontok?
i used Avast scan my infected folder,but there are no result.
Maybe this variant is not on the virus database… 
Can you send a sample to virus @ avast.com ?
how to send?
You can zip and password the files… Inform a link to this thread and the password used.
You can send the files to Chest and, from there, resend to Alwil for analysis.
Or you can use Alwil FTP server as a second way to transfer only big files. Upload them to ftp://ftp.avast.com/incoming (please, note that you won’t have READ access to the ftp server, just write - so you won’t even be able to see what you’ve just uploaded).