ituneshelper infects usb keys

Hello,

I have a virus which transforms files in hidden files and creates shortcut for all the files.
It’s seems to go with an ituneshelper I see on the usb keys.
Now, all new usb keys get infected if I connect them on my computer.
Avast don’t see any virus.
In the internet I saw some tools about it. But Avast says these tools are virus and blocks the download.
Have you information about that ?
Thanks.

start with this, follow instructions http://forum.avast.com/index.php?topic=53253.msg998925#msg998925

attach log

then continue with this…

follow instructions and attach logs (not copy and paste) http://forum.avast.com/index.php?topic=53253.0

run in order listed
AdwCleaner / Malwarebytes / OTL / aswMBR

when done, removal experts will be notified and help you
when finish, all tools used will be removed

Monitoring…