An anonymous researcher created a massive botnet by hijacking about 420,000 Internet-accessible embedded devices with default or no login passwords and used it to map the entire Internet. The botnet, which was dubbed Carna after the Roman goddess of physical health, ran between March and December 2012, and was used to perform "the largest and most comprehensive IPv4 [Internet Protocol version 4] census ever," the researcher said Sunday on a website dedicated to the project.