The program SNOW is used to conceal messages in ASCII text by appending whitespace to the end of lines. Because spaces and tabs are generally not visible in text viewers, the message is effectively hidden from casual observers. And if the built-in encryption is used, the message cannot be read even if it is detected.
SNOW exploits the Steganographic Nature Of Whitespace. Locating trailing whitespace in text is like finding a polar bear in a snowstorm (which, by the way, explains the logo). And it uses the ICE encryption algorithm, so the name is thematically consistent.
As of 16 June 2013, SNOW is available under an Apache 2.0 licece. The usual conditions apply, but if you find SNOW useful for anything, the author would love to hear about it.
Prior to 22 November 1998 the DOS version, contained in snowdos.zip, had a bug affecting encryption. Files concealed with encryption using the DOS version could not be decrypted by the other versions, and vice versa. The bug was caused by bit-shifting of 16-bit variables in DOS. This has now been fixed.
The source version, when compiled under Unix, also had a bug where it could not read data concealed by the DOS version, owing to the carriage return character appended by DOS. This has also been fixed as of 22 November 1998.