whatever is the script, one needs to use available techniques to prevent the spam. if you are looking for a free script then MyBB has good quality add-ons to combat spam
I'd recommend MyBB with one or more of its spam prevention plugins such as StopForumSpam. You can also setup reCAPTCHA and security questions to stop the bots.
You're probably gonna get spam no matter what. Forum admin: How to deal with SPAM? - maybe this will help with keeping spam away. As for what script to use, I'd go with Xenforo or vBulletin
vbulletin is the most powerful forum cms it has mods to stop spam akismet is built in and also you can add stopforumspam key in it
You can add those features to just about any other forum software, but vBulletin is very nice if it fits your budget.
I had to shut down my board because I couldn't fight spam bots anymore. There was some issue with re-captcha plugin for mybb so I had to forget about that and stopforumspam plugin was causing some issues also. People couldn't registered, even my IP was blocked and I have a dynamic one. So I had to disable it, finally I gave up and closed down the board. I believe the best way to fight the spam is a custom written captcha-like system with 'clever' question like 'what day is it today' or 'who is the president of usa' and such. So if you invest in custom programming, it doesn't matter what forum software you use.
I'll agree that all scripts will get spammed to some extent. I would go with vBulletin or xenforo for paid solutions.
If you are looking for a free script, I would go with MyBB. It is easy to use and has a huge support community should you need help. They also develop a lot of add-ons for it, considering how large the support community is. I don't have any experience with paid forum software, but VBulletin or Xenforo make some nice choices. They seem to be the two that I keep seeing people using the most.
vBulletin is definitely the cream of the crop if you're looking for a long-term solution. Their support is excellent and the variety of themes is impressive. Security is top-notch as well. When you're looking at free ones, SMF has some useful anti-spam plugins.
I will go with Ipboard and vBulletin for the premium solutions, and MyBB for the free easy user friendly.
Mybb rules I have used it 2 yrs now it is great I will not use anything thing else nothing else can touch it. SMF is dying not many templates skins any more support is not what it use to be everyone is switching to Mybb
If you are asking about which forum software to use to prevent spam then try Website Toolbox. Gives you security editing options along with the forum. It is quite cheap, and you can suggest a good deal of features to the forum team, including what ever security features to prevent spam you would like.