further to nihil's account
the spammer are allowed to set an account
ideally we should be able to stop certain sections of the registration form until they have been accepted, AND have posted

but downside is that without th espam additions to the registration form, we would have to accept them into the forum AND have them post their tat

on Taz, also a phpbb, we set a security question into the registration procedure, that requires input to the answer to allow the registration to complete

this has, so far , stopped damn nigh all spam accounts on Taz
AK's site is an easier one to control too, as he set it mainly for friends, who are local to him [USA] so we can add several address endings to the ban lists

but it does continue to be a PITA

one other in the phpbb v vbb issue
does anyone have experience of Web Wiz Forums ??
as I also admin one of those too at http://www.motorbike-search-engine.co.uk/forum/
and I don't know how, but we've had only ONE spam account since creation

and we don't know how we did it either