Brute force a ciphered message? I wrote my own cipher to encrypt messages. I would like to test a sample ciphered message to see how strong it is. Are there any tools for such task either in Windows or Linux ?
There's no way to verify the strength of a cipher in any automated way, especially given only the ciphertext. Attacking the construction of a cipher is an inherantly intellectual process, which does not fit well to the qualities of computer analysis.

For example, I could write a cipher such that $f(m) = rand(0,n)$ where $n$ is the largest integer representable in $sizeof(m)*8$ bits, and any automated analysis would say "this is an awesome cipher", but a human would immediately realise that it's totally useless.

If you're writing your own ciphers for real usage, I have only one piece of advice: don't.

Creating your own ciphers is fun, and it can give you a learning experience if you're actually doing it based on constructions you understand, but the resulting cipher should never ever go anywhere near a production system. Experts put their ciphers through years (decades, even) of peer review before they're adopted by anyone. If your goal is to learn, do so by breaking ciphers.