This is a family of stealth multipartite fast infecting viruses originating from Australia. There are at least five variants, sizes ranging from 2 to 3 kB.
Once detected, the F-Secure security product will automatically disinfect the suspect file by either deleting it or renaming it.
One of the variants generates an endless loop to the partition table, making PC crash when it tries to boot from a clean floppy which has MS-DOS v4.0 - 7.0. To overcome this, use PC-DOS 7.0, MS-DOS 3.3x or a non-DOS boot floppy. Contact F-Secure anti-virus support for further instructions.
Note: Rainbow is also an alias for the WordMacro/Colors virus.
Description Created: Mikko Hypponen, F-Secure