Unfortunately, it is virtually impossible to create an automated system to spammers. Like other 'Cyber-Offenders', they're always one step ahead. People who spamming filters such systems are nearly always playing catch-up.

I do (or used to) frequent forums which have high levels of traffic yet have no spamming problems. These forums are all registration moderated. I know it's not ideal, but at least you're not relying on filters.