user - What's the best way to prevent spam accounts -

i have problem literally thousands of spam accounts being registered. i've use captcha on registration form, check user's ip hasn't registered account in last 10 minutes, routinely go in clear out hundreds of accounts suspicious or post spam or in way related accounts post spam, doesn't seem make dent.

so other, creative ways can prevent spam accounts being created? i'd avoid e-mail confirmation because e-mails send don't through user. also, if they're manually entering captcha , using hundreds of different ip addresses, i"m not sure e-mail confirmation work either.

any , ideas appreciated.

in addition you're doing have form field in registration form hidden using css. name don't need wouldn't out of place on registration form. if has value in it, reject registration.

<style>     input.form-tel {         display:none;     } </style>  <input type="text" name="telephone" class="form-tel"> 

this prevent bot submissions. if you've got captcha it's there teams of spammers working on site. questions need ask are:

• why spammers targeting site? if can post content includes urls linked other sites should disallow new users until they're trusted?
• is there pattern details provide, can flag accounts approval if suspicious based on number of rules?
• can address issue of emails not getting through using more reliable provider? enable parts of account until email address has been confirmed can continue use of site's features. example, publishing disabled until they've confirmed address.