ExtraAntivirus is a new rogue. It belongs to the same family as Virus Sweeper, Ultra Antivir 2009, Virusdoctor, VirusMelt, VirusAlarm.
Extra Antivirus comes from fake online scanners. Extra Antivirus drops many files on the system with different filenames taken from a dictionary. These files are not Win32 executables and are detected as infections to scare users.
BleepingComputer Removal Guide.