Analyzing AT&T's Anti-Anti-Spam Patent

An anonymous reader writes "Dan Gillmor is reporting in his eJournal taken, in turn, from Gregory Aharonian: AT&T has apparently been awarded a patent for circumventing certain spam filters, thereby providing slimeball spammers with yet a bigger hammer!" The patent covers "A system and method for circumventing schemes that use duplication detection to detect and block unsolicited e-mail (spam.)", although it's unclear exactly what AT&T want it for.