I am aware of spam in forum and not very happy about it. I am trying to deal with it over time, IP.Board spam filter doesn't seem to work very well
Perhaps you might consider using a couple of moderators to handle the obvious spam. It would save you policing the forums and diverting your time resources to managing this irritation. I would also suggest using a system like ZBBlock to trap automated posting systems like Xrumer and Forum Poster 3: it can also block IP addresses by country and mitigate against people trying to use SQL injection attacks and the like. Several IP Board forums I used to run were inundated with probes and scans from various bad agents, particularly China, until I started using ZBB.
I would also suggest imposing restrictions on first-time posters, something that be easily implemented in IPB. For example, restricting a first-time user to having their first few posts moderated.
I generally found that while IP Board's inbuilt systems could handle a certain kind of abuse, other measures were needed upstream to deal with the other idiots.