You may wonder what is considered as an autorun worm? Autorun worm is a worm that infects your PC through removable device such as USB thumb drive or CD/DVD. In addition, it has a file called autorun.inf which contains code to run malicious program. If your PC does not block autorun, the autorun worm will executes once you double click the drive letter of your removable device. Microsoft Windows Operating System does not disable autorun by default.