How to disallow visitors from known proxy servers?

[tntpower]

Some people (not robots) keep posting inappropriate threads in my forum. I banned their IPs but they use proxy to come back.

How to disallow all visitors from known proxy servers? The number of proxy is very large and I do not think it is possible to have a list of all of them.

Do I need to buy service like [maxmind.com...] and integrate it with Apache or is there some handy solution?

Thank you

[g1smd]

One way is to detect X-FORWARDED-FOR I believe, but there's a risk of cutting out a lot of legitimite users too.

[caribguy]

Relying on X-Forwarded-For will for example deny all users who access your site over a satellite linkup.

[tntpower]

I did a quick search and it seems that service like maxmind provides is the only robust solution. too bad.

[Caterham]

May be
[en.wikipedia.org...]
is a good point to start. But that's the opposite of a handy solution, I think.

I don't know how large your forum is, but may be you can force registration with e-mail validation. That won't prevent them from posting inappropriate threads, of course, but may be opening new accounts after you blocked the old ones annoys them after some time...

[wilderness]

try stayinvisible dot com.
Enough numbers there to take up your days and nights for a couple of year ;)

[jecasc]

Are you sure they even use proxies? All most people have to do to get a new IP is to switch their DSL modem off and on again.

[g1smd]

Because of latency concerns, satellite ISPs often pull and cache images, CSS, and JS as soon as you start downloading the HTML for a page, and then serve it to you via that proxy.