A Stub IOS is an IOS that serves no purpose other than a placeholder. They are typically released by Nintendo in order to overwrite any existing version of an IOS and render it unusable for piracy or homebrew purposes.
Most stub IOSes are version 65280; this is version 255.0. Most homebrew IOSes use version 65535 (255.255) to prevent Nintendo from updating them.
Stub IOSes generally have 3 contents: a 0x40 byte build tag, and two shared contents, which depend on the variant.
There are several variants of stub IOSes.
The first stub IOSes were released in 3.3rev03 to IOS4, IOS10, IOS11 and IOS20, with a size of 245760. They were built by someone named
yasuh-to@TONKAT. This variant was also used for the IOS30 stub distributed in 3.4.
The 4.0 variant has a size of 229376, and was built by
The 4.2 stubs, including both IOS60 and the cIOS stubs, also have a size of 229376 just like the 4.0 variant, but were built by
kenshu@MAENORYU. The second content is identical to that in the 4.0 variant, but the third content is different.
IOS70 has size 245760, but has nothing in common with the 2008 variant of stub IOSes. It was built by
IOS254 also has size 245760, but it has nothing common with IOS70 or the 2008 stubs. It was built by