You could make a very small plugin so only email addresses on the mailing list can be used to register new members; this could be combined with other "defences". It'd stop most of the automated Wordpress registration scripts that are out there; though it obviously wouldn't hold out a determined attacker since all they have to do is register with the mailing list to be allowed in...
http://codex.wordpress.org/Plugin_API/Filter_Reference/registration_errors
Cheers,
Benjie.--
Please post to: Hampshire@???
Web Interface:
https://mailman.lug.org.uk/mailman/listinfo/hampshire
LUG URL:
http://www.hantslug.org.uk
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