I had lots of forum spam this is what I did to stop it:
Installed GlowHost Spamomatic and configure it
This blocks on average 50 email addresses a day from registering.
Enable VBOptions -> Human Verification Options for everything except post
Enable reCaptcha in Settings->Human Verification Manager
This solved 95% of the spam. After I got CloudFlare Free edition and set security mode to Medium and I forced enhanced authentication on all IP's coming from Russia, Ukraine & Romania and we now have ZERO SPAM!
To remove the blog tab go to VbAdminCP -> Settings -> Navigation Manager and if you want to disable blog completely disable it in Products/Plugins
I'm not an expert on anything but I know this worked great for us