It's an unfortunate fact that when you run a successful site, you attract unwanted users posting spam on your site. IP.Board has always been incredibly pro-active in preventing spam users from signing up by making use of built in tools such as the question and answer challenge, spam monitoring service and CAPTCHA systems.
I'd like to take a moment to talk about some enhancements we've made in IP.Board 3.4.0 to help prevent unwanted posts and spam.
Spam Monitoring Improvements
We've further enhanced the spam monitoring service in IP.Board 3.4.0 by adding a new option: "Do not permit the user to register an account". This reduces the amount of clean up you need to do after a new wave of attempted spam user sign-ups.
Furthermore, the "flag a member as a spammer" tool optionally deletes posted content rather than simply hiding them further reducing the amount of work needed to maintain your community. 
We have also totally reworked our spammer-detection logic behind the scenes to make the spam monitoring service detect spammers more quickly. In addition to internal changes, we are also looking at direct integration with services like Project Honey Pot and others. The great thing about the spam monitoring service is that we can make improvements on our side that are instantly beneficial to your community.
keyCAPTCHA Integration
IP.Board has made good use of the popular reCAPTCHA service to limit the number of "bots" that sign up to your forum with the intent of posting spam. The idea being that a slightly jumbled selection of letters is easy enough for a human to read but more difficult for a computer program. However, some do find that the CAPTCHA images are becoming increasingly complex to keep up with more intelligently written programs to defeat them.
KeyCAPTCHA takes a novel approach to this problem by using images instead of letters and numbers. You simply arrange a few large pieces of a very simple puzzle to complete an image.
You don't need to be completely accurate when building the image, either.
This is now an option in the IP.Board Admin CP. Should you wish to enable it, you'll need to register an account with keyCAPTCHA. The link for this is contained in the setting form and is very straight forward.
As always, we look for new ways to help make running your community a little easier and we look forward to helping you keep those spammers at bay!
By Matt