Well... Bayes certainly works on Russian words. Most Russian spam is correctly recognized by my Bayes-enabled SpamAssassin. If you DON'T want any Russian email you can make a rule for the Cyrillic character set, but to write custom rules against Russian spam would be difficult.
Recent versions of SpamAssassin (starting with 3.0, I guess) strip all chars with codes > 128 before feeding message to bayes.
Eugene
