.CISO File Extension
What is a CISO file?
CD or DVD disc image image container format designed for efficient storage and distribution of CD/DVD images; contains an exact duplicate of data from the original disc, without unnecessary "junk data."
CISO files are commonly used to store Wii games. The CISO file is the same as an .ISO file except it is compact, which means it removes all the "junk data" used to pad Wii games to make them appear as full discs. The CISO format features password based encryption and digital signing for software distribution.