Paraphrasing the article, it would be for the server to use undefined behavior in the _authentic_ clients to determine that they were in fact authentic. In this

Paraphrasing the article, it would be for the server to use undefined behavior in the _authentic_ clients to determine that they were in fact authentic. In this case, a buffer overflow doesn't appear to crash the client, but lets the server know that it's talking to a legitimate client. That's quite clever.