Most of the viruses which are widespread due to OS like Windows can be easily smashed in OS like Ubuntu ;)

Steps to success:

cd /media/<your-usb-drive>
sudo chmod 777 *.*

Common viruses:

• Autorun.inf
• Ravmon.exe
• New Folder.exe
• svchost.exe
• Heap41a
• NewFolder.exe
• System
• RECYCLER

…or any other exe file which may be suspicious.

Remove them:

sudo rm -rf *.exe
sudo rm -rf Autorun.inf
sudo rm -rf RECYCLER

P.S: If step 2 did not help try sudo chmod 777 *