  Although the problem of spam classification seems to be solved, there are
still vulnerabilities in the current spam filters that could be easily
exploited. We present one such vulnerability, in which one could replace some
characters with corresponding characters from a different alphabet. These
characters are visually similar, yet have a different Unicode encoding. With
this approach spammers can create messages that bypass existing spam filters.
Moreover, we show that this approach can be used to avoid plagiarism detection,
and in other applications that use natural language processing for automatic
analysis of text documents.
