Hi,<p>I'm getting a large number of scam/spam messages being sent to users on my site. I have the usual deterrents in place (captchas, etc) but was wondering if there is a good API out there I can query to see if a user's IP address is being proxied or if they are known scammers/spammers/bad people from their ip address.<p>Thanks!
I don't know any services, but this might be a good place to start looking: <a href="http://whatismyipaddress.com/blacklist-check" rel="nofollow">http://whatismyipaddress.com/blacklist-check</a>.<p>There are a number of links to various IP blacklist providers.
Well behaving proxy servers will send X-Forwarded-For and other extra headers along with the request. Maybe the spammers actually use zombie machines (that don't send this), but worth checking at least.<p>Most individual spammers do at least one thing that makes it easy to identify them. Maybe they submit forms 10x faster than any human? Maybe no referer? A unique user agent?
I wrote a script that runs every 15 minutes and checks the IPs of new users against Stop Forum Spam's API here:<p><a href="http://www.stopforumspam.com/apis" rel="nofollow">http://www.stopforumspam.com/apis</a><p>It's caught the significant majority of spammers, giving me some time to write other spam protection checks.