usually virus or malwares attack the autorun.inf on anytype of removable drives. When we insert the drives to the computer it will autoplay and the autorun.inf files has been already infected with the virus, so the virus gains control over the drive and copy itself to the computer, hence this process goes on and the virus spreads. To overcome this , we should disable autoplay features of removable drives. You can use tweak UI tool to turn off this feature. or use registry editor to turn of autoplay features on removable drives. the easiest way is to press the SHIFT button while inserting the drive and hold the SHIFT key after it is ready to browse. don't double click the removable drive, use right click and open to browse the pendrive.