An unauthorized user gaining physical access to a computer is most likely able to directly download data from it. They may also compromise security by making operating system modifications, installing software worms, keyloggers, or covert listening devices. Even when the system is protected by standard security measures, these may be able to be by passed by booting another operating system or tool from a CD-ROM or other bootable media. Disk encryption and Trusted Platform Module are designed to prevent these attacks.