Don't block them, degrade their performance to annoy them out of your platform. Or treat them the way you would any spambot,add registration difficulty,cumulati

Don't block them, degrade their performance to annoy them out of your platform. Or treat them the way you would any spambot,add registration difficulty,cumulative but minimal interaction cost(performance,financial,points,etc...) and as a last resort ban or set restrictions on their connectivity network (subnet,isp,email provider, vpn provider,asn,country,etc...)